/*
 * guest access functions
 *
 * Copyright IBM Corp. 2014
 *
 */

#include <linux/vmalloc.h>
#include <linux/err.h>
#include <asm/pgtable.h>
#include <asm/gmap.h>
#include "kvm-s390.h"
#include "gaccess.h"
#include <asm/switch_to.h>

union asce {
        unsigned long val;
        struct {
                unsigned long origin : 52; /* Region- or Segment-Table Origin */
                unsigned long    : 2;
                unsigned long g  : 1; /* Subspace Group Control */
                unsigned long p  : 1; /* Private Space Control */
                unsigned long s  : 1; /* Storage-Alteration-Event Control */
                unsigned long x  : 1; /* Space-Switch-Event Control */
                unsigned long r  : 1; /* Real-Space Control */
                unsigned long    : 1;
                unsigned long dt : 2; /* Designation-Type Control */
                unsigned long tl : 2; /* Region- or Segment-Table Length */
        };
};

enum {
        ASCE_TYPE_SEGMENT = 0,
        ASCE_TYPE_REGION3 = 1,
        ASCE_TYPE_REGION2 = 2,
        ASCE_TYPE_REGION1 = 3
};

union region1_table_entry {
        unsigned long val;
        struct {
                unsigned long rto: 52;/* Region-Table Origin */
                unsigned long    : 2;
                unsigned long p  : 1; /* DAT-Protection Bit */
                unsigned long    : 1;
                unsigned long tf : 2; /* Region-Second-Table Offset */
                unsigned long i  : 1; /* Region-Invalid Bit */
                unsigned long    : 1;
                unsigned long tt : 2; /* Table-Type Bits */
                unsigned long tl : 2; /* Region-Second-Table Length */
        };
};

union region2_table_entry {
        unsigned long val;
        struct {
                unsigned long rto: 52;/* Region-Table Origin */
                unsigned long    : 2;
                unsigned long p  : 1; /* DAT-Protection Bit */
                unsigned long    : 1;
                unsigned long tf : 2; /* Region-Third-Table Offset */
                unsigned long i  : 1; /* Region-Invalid Bit */
                unsigned long    : 1;
                unsigned long tt : 2; /* Table-Type Bits */
                unsigned long tl : 2; /* Region-Third-Table Length */
        };
};

struct region3_table_entry_fc0 {
        unsigned long sto: 52;/* Segment-Table Origin */
        unsigned long    : 1;
        unsigned long fc : 1; /* Format-Control */
        unsigned long p  : 1; /* DAT-Protection Bit */
        unsigned long    : 1;
        unsigned long tf : 2; /* Segment-Table Offset */
        unsigned long i  : 1; /* Region-Invalid Bit */
        unsigned long cr : 1; /* Common-Region Bit */
        unsigned long tt : 2; /* Table-Type Bits */
        unsigned long tl : 2; /* Segment-Table Length */
};

struct region3_table_entry_fc1 {
        unsigned long rfaa : 33; /* Region-Frame Absolute Address */
        unsigned long    : 14;
        unsigned long av : 1; /* ACCF-Validity Control */
        unsigned long acc: 4; /* Access-Control Bits */
        unsigned long f  : 1; /* Fetch-Protection Bit */
        unsigned long fc : 1; /* Format-Control */
        unsigned long p  : 1; /* DAT-Protection Bit */
        unsigned long co : 1; /* Change-Recording Override */
        unsigned long    : 2;
        unsigned long i  : 1; /* Region-Invalid Bit */
        unsigned long cr : 1; /* Common-Region Bit */
        unsigned long tt : 2; /* Table-Type Bits */
        unsigned long    : 2;
};

union region3_table_entry {
        unsigned long val;
        struct region3_table_entry_fc0 fc0;
        struct region3_table_entry_fc1 fc1;
        struct {
                unsigned long    : 53;
                unsigned long fc : 1; /* Format-Control */
                unsigned long    : 4;
                unsigned long i  : 1; /* Region-Invalid Bit */
                unsigned long cr : 1; /* Common-Region Bit */
                unsigned long tt : 2; /* Table-Type Bits */
                unsigned long    : 2;
        };
};

struct segment_entry_fc0 {
        unsigned long pto: 53;/* Page-Table Origin */
        unsigned long fc : 1; /* Format-Control */
        unsigned long p  : 1; /* DAT-Protection Bit */
        unsigned long    : 3;
        unsigned long i  : 1; /* Segment-Invalid Bit */
        unsigned long cs : 1; /* Common-Segment Bit */
        unsigned long tt : 2; /* Table-Type Bits */
        unsigned long    : 2;
};

struct segment_entry_fc1 {
        unsigned long sfaa : 44; /* Segment-Frame Absolute Address */
        unsigned long    : 3;
        unsigned long av : 1; /* ACCF-Validity Control */
        unsigned long acc: 4; /* Access-Control Bits */
        unsigned long f  : 1; /* Fetch-Protection Bit */
        unsigned long fc : 1; /* Format-Control */
        unsigned long p  : 1; /* DAT-Protection Bit */
        unsigned long co : 1; /* Change-Recording Override */
        unsigned long    : 2;
        unsigned long i  : 1; /* Segment-Invalid Bit */
        unsigned long cs : 1; /* Common-Segment Bit */
        unsigned long tt : 2; /* Table-Type Bits */
        unsigned long    : 2;
};

union segment_table_entry {
        unsigned long val;
        struct segment_entry_fc0 fc0;
        struct segment_entry_fc1 fc1;
        struct {
                unsigned long    : 53;
                unsigned long fc : 1; /* Format-Control */
                unsigned long    : 4;
                unsigned long i  : 1; /* Segment-Invalid Bit */
                unsigned long cs : 1; /* Common-Segment Bit */
                unsigned long tt : 2; /* Table-Type Bits */
                unsigned long    : 2;
        };
};

enum {
        TABLE_TYPE_SEGMENT = 0,
        TABLE_TYPE_REGION3 = 1,
        TABLE_TYPE_REGION2 = 2,
        TABLE_TYPE_REGION1 = 3
};

union page_table_entry {
        unsigned long val;
        struct {
                unsigned long pfra : 52; /* Page-Frame Real Address */
                unsigned long z  : 1; /* Zero Bit */
                unsigned long i  : 1; /* Page-Invalid Bit */
                unsigned long p  : 1; /* DAT-Protection Bit */
                unsigned long co : 1; /* Change-Recording Override */
                unsigned long    : 8;
        };
};

/*
 * vaddress union in order to easily decode a virtual address into its
 * region first index, region second index etc. parts.
 */
union vaddress {
        unsigned long addr;
        struct {
                unsigned long rfx : 11;
                unsigned long rsx : 11;
                unsigned long rtx : 11;
                unsigned long sx  : 11;
                unsigned long px  : 8;
                unsigned long bx  : 12;
        };
        struct {
                unsigned long rfx01 : 2;
                unsigned long       : 9;
                unsigned long rsx01 : 2;
                unsigned long       : 9;
                unsigned long rtx01 : 2;
                unsigned long       : 9;
                unsigned long sx01  : 2;
                unsigned long       : 29;
        };
};

/*
 * raddress union which will contain the result (real or absolute address)
 * after a page table walk. The rfaa, sfaa and pfra members are used to
 * simply assign them the value of a region, segment or page table entry.
 */
union raddress {
        unsigned long addr;
        unsigned long rfaa : 33; /* Region-Frame Absolute Address */
        unsigned long sfaa : 44; /* Segment-Frame Absolute Address */
        unsigned long pfra : 52; /* Page-Frame Real Address */
};

union alet {
        u32 val;
        struct {
                u32 reserved : 7;
                u32 p        : 1;
                u32 alesn    : 8;
                u32 alen     : 16;
        };
};

union ald {
        u32 val;
        struct {
                u32     : 1;
                u32 alo : 24;
                u32 all : 7;
        };
};

struct ale {
        unsigned long i      : 1; /* ALEN-Invalid Bit */
        unsigned long        : 5;
        unsigned long fo     : 1; /* Fetch-Only Bit */
        unsigned long p      : 1; /* Private Bit */
        unsigned long alesn  : 8; /* Access-List-Entry Sequence Number */
        unsigned long aleax  : 16; /* Access-List-Entry Authorization Index */
        unsigned long        : 32;
        unsigned long        : 1;
        unsigned long asteo  : 25; /* ASN-Second-Table-Entry Origin */
        unsigned long        : 6;
        unsigned long astesn : 32; /* ASTE Sequence Number */
} __packed;

struct aste {
        unsigned long i      : 1; /* ASX-Invalid Bit */
        unsigned long ato    : 29; /* Authority-Table Origin */
        unsigned long        : 1;
        unsigned long b      : 1; /* Base-Space Bit */
        unsigned long ax     : 16; /* Authorization Index */
        unsigned long atl    : 12; /* Authority-Table Length */
        unsigned long        : 2;
        unsigned long ca     : 1; /* Controlled-ASN Bit */
        unsigned long ra     : 1; /* Reusable-ASN Bit */
        unsigned long asce   : 64; /* Address-Space-Control Element */
        unsigned long ald    : 32;
        unsigned long astesn : 32;
        /* .. more fields there */
} __packed;

int ipte_lock_held(struct kvm_vcpu *vcpu)
{
        if (vcpu->arch.sie_block->eca & 1) {
                int rc;

                read_lock(&vcpu->kvm->arch.sca_lock);
                rc = kvm_s390_get_ipte_control(vcpu->kvm)->kh != 0;
                read_unlock(&vcpu->kvm->arch.sca_lock);
                return rc;
        }
        return vcpu->kvm->arch.ipte_lock_count != 0;
}

static void ipte_lock_simple(struct kvm_vcpu *vcpu)
{
        union ipte_control old, new, *ic;

        mutex_lock(&vcpu->kvm->arch.ipte_mutex);
        vcpu->kvm->arch.ipte_lock_count++;
        if (vcpu->kvm->arch.ipte_lock_count > 1)
                goto out;
retry:
        read_lock(&vcpu->kvm->arch.sca_lock);
        ic = kvm_s390_get_ipte_control(vcpu->kvm);
        do {
                old = READ_ONCE(*ic);
                if (old.k) {
                        read_unlock(&vcpu->kvm->arch.sca_lock);
                        cond_resched();
                        goto retry;
                }
                new = old;
                new.k = 1;
        } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
        read_unlock(&vcpu->kvm->arch.sca_lock);
out:
        mutex_unlock(&vcpu->kvm->arch.ipte_mutex);
}

static void ipte_unlock_simple(struct kvm_vcpu *vcpu)
{
        union ipte_control old, new, *ic;

        mutex_lock(&vcpu->kvm->arch.ipte_mutex);
        vcpu->kvm->arch.ipte_lock_count--;
        if (vcpu->kvm->arch.ipte_lock_count)
                goto out;
        read_lock(&vcpu->kvm->arch.sca_lock);
        ic = kvm_s390_get_ipte_control(vcpu->kvm);
        do {
                old = READ_ONCE(*ic);
                new = old;
                new.k = 0;
        } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
        read_unlock(&vcpu->kvm->arch.sca_lock);
        wake_up(&vcpu->kvm->arch.ipte_wq);
out:
        mutex_unlock(&vcpu->kvm->arch.ipte_mutex);
}

static void ipte_lock_siif(struct kvm_vcpu *vcpu)
{
        union ipte_control old, new, *ic;

retry:
        read_lock(&vcpu->kvm->arch.sca_lock);
        ic = kvm_s390_get_ipte_control(vcpu->kvm);
        do {
                old = READ_ONCE(*ic);
                if (old.kg) {
                        read_unlock(&vcpu->kvm->arch.sca_lock);
                        cond_resched();
                        goto retry;
                }
                new = old;
                new.k = 1;
                new.kh++;
        } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
        read_unlock(&vcpu->kvm->arch.sca_lock);
}

static void ipte_unlock_siif(struct kvm_vcpu *vcpu)
{
        union ipte_control old, new, *ic;

        read_lock(&vcpu->kvm->arch.sca_lock);
        ic = kvm_s390_get_ipte_control(vcpu->kvm);
        do {
                old = READ_ONCE(*ic);
                new = old;
                new.kh--;
                if (!new.kh)
                        new.k = 0;
        } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
        read_unlock(&vcpu->kvm->arch.sca_lock);
        if (!new.kh)
                wake_up(&vcpu->kvm->arch.ipte_wq);
}

void ipte_lock(struct kvm_vcpu *vcpu)
{
        if (vcpu->arch.sie_block->eca & 1)
                ipte_lock_siif(vcpu);
        else
                ipte_lock_simple(vcpu);
}

void ipte_unlock(struct kvm_vcpu *vcpu)
{
        if (vcpu->arch.sie_block->eca & 1)
                ipte_unlock_siif(vcpu);
        else
                ipte_unlock_simple(vcpu);
}

static int ar_translation(struct kvm_vcpu *vcpu, union asce *asce, ar_t ar,
                          enum gacc_mode mode)
{
        union alet alet;
        struct ale ale;
        struct aste aste;
        unsigned long ald_addr, authority_table_addr;
        union ald ald;
        int eax, rc;
        u8 authority_table;

        if (ar >= NUM_ACRS)
                return -EINVAL;

        save_access_regs(vcpu->run->s.regs.acrs);
        alet.val = vcpu->run->s.regs.acrs[ar];

        if (ar == 0 || alet.val == 0) {
                asce->val = vcpu->arch.sie_block->gcr[1];
                return 0;
        } else if (alet.val == 1) {
                asce->val = vcpu->arch.sie_block->gcr[7];
                return 0;
        }

        if (alet.reserved)
                return PGM_ALET_SPECIFICATION;

        if (alet.p)
                ald_addr = vcpu->arch.sie_block->gcr[5];
        else
                ald_addr = vcpu->arch.sie_block->gcr[2];
        ald_addr &= 0x7fffffc0;

        rc = read_guest_real(vcpu, ald_addr + 16, &ald.val, sizeof(union ald));
        if (rc)
                return rc;

        if (alet.alen / 8 > ald.all)
                return PGM_ALEN_TRANSLATION;

        if (0x7fffffff - ald.alo * 128 < alet.alen * 16)
                return PGM_ADDRESSING;

        rc = read_guest_real(vcpu, ald.alo * 128 + alet.alen * 16, &ale,
                             sizeof(struct ale));
        if (rc)
                return rc;

        if (ale.i == 1)
                return PGM_ALEN_TRANSLATION;
        if (ale.alesn != alet.alesn)
                return PGM_ALE_SEQUENCE;

        rc = read_guest_real(vcpu, ale.asteo * 64, &aste, sizeof(struct aste));
        if (rc)
                return rc;

        if (aste.i)
                return PGM_ASTE_VALIDITY;
        if (aste.astesn != ale.astesn)
                return PGM_ASTE_SEQUENCE;

        if (ale.p == 1) {
                eax = (vcpu->arch.sie_block->gcr[8] >> 16) & 0xffff;
                if (ale.aleax != eax) {
                        if (eax / 16 > aste.atl)
                                return PGM_EXTENDED_AUTHORITY;

                        authority_table_addr = aste.ato * 4 + eax / 4;

                        rc = read_guest_real(vcpu, authority_table_addr,
                                             &authority_table,
                                             sizeof(u8));
                        if (rc)
                                return rc;

                        if ((authority_table & (0x40 >> ((eax & 3) * 2))) == 0)
                                return PGM_EXTENDED_AUTHORITY;
                }
        }

        if (ale.fo == 1 && mode == GACC_STORE)
                return PGM_PROTECTION;

        asce->val = aste.asce;
        return 0;
}

struct trans_exc_code_bits {
        unsigned long addr : 52; /* Translation-exception Address */
        unsigned long fsi  : 2;  /* Access Exception Fetch/Store Indication */
        unsigned long      : 6;
        unsigned long b60  : 1;
        unsigned long b61  : 1;
        unsigned long as   : 2;  /* ASCE Identifier */
};

enum {
        FSI_UNKNOWN = 0, /* Unknown wether fetch or store */
        FSI_STORE   = 1, /* Exception was due to store operation */
        FSI_FETCH   = 2  /* Exception was due to fetch operation */
};

enum prot_type {
        PROT_TYPE_LA   = 0,
        PROT_TYPE_KEYC = 1,
        PROT_TYPE_ALC  = 2,
        PROT_TYPE_DAT  = 3,
};

static int trans_exc(struct kvm_vcpu *vcpu, int code, unsigned long gva,
                     ar_t ar, enum gacc_mode mode, enum prot_type prot)
{
        struct kvm_s390_pgm_info *pgm = &vcpu->arch.pgm;
        struct trans_exc_code_bits *tec;

        memset(pgm, 0, sizeof(*pgm));
        pgm->code = code;
        tec = (struct trans_exc_code_bits *)&pgm->trans_exc_code;

        switch (code) {
        case PGM_PROTECTION:
                switch (prot) {
                case PROT_TYPE_ALC:
                        tec->b60 = 1;
                        /* FALL THROUGH */
                case PROT_TYPE_DAT:
                        tec->b61 = 1;
                        break;
                default: /* LA and KEYC set b61 to 0, other params undefined */
                        return code;
                }
                /* FALL THROUGH */
        case PGM_ASCE_TYPE:
        case PGM_PAGE_TRANSLATION:
        case PGM_REGION_FIRST_TRANS:
        case PGM_REGION_SECOND_TRANS:
        case PGM_REGION_THIRD_TRANS:
        case PGM_SEGMENT_TRANSLATION:
                /*
                 * op_access_id only applies to MOVE_PAGE -> set bit 61
                 * exc_access_id has to be set to 0 for some instructions. Both
                 * cases have to be handled by the caller.
                 */
                tec->addr = gva >> PAGE_SHIFT;
                tec->fsi = mode == GACC_STORE ? FSI_STORE : FSI_FETCH;
                tec->as = psw_bits(vcpu->arch.sie_block->gpsw).as;
                /* FALL THROUGH */
        case PGM_ALEN_TRANSLATION:
        case PGM_ALE_SEQUENCE:
        case PGM_ASTE_VALIDITY:
        case PGM_ASTE_SEQUENCE:
        case PGM_EXTENDED_AUTHORITY:
                /*
                 * We can always store exc_access_id, as it is
                 * undefined for non-ar cases. It is undefined for
                 * most DAT protection exceptions.
                 */
                pgm->exc_access_id = ar;
                break;
        }
        return code;
}

static int get_vcpu_asce(struct kvm_vcpu *vcpu, union asce *asce,
                         unsigned long ga, ar_t ar, enum gacc_mode mode)
{
        int rc;
        struct psw_bits psw = psw_bits(vcpu->arch.sie_block->gpsw);

        if (!psw.t) {
                asce->val = 0;
                asce->r = 1;
                return 0;
        }

        if (mode == GACC_IFETCH)
                psw.as = psw.as == PSW_AS_HOME ? PSW_AS_HOME : PSW_AS_PRIMARY;

        switch (psw.as) {
        case PSW_AS_PRIMARY:
                asce->val = vcpu->arch.sie_block->gcr[1];
                return 0;
        case PSW_AS_SECONDARY:
                asce->val = vcpu->arch.sie_block->gcr[7];
                return 0;
        case PSW_AS_HOME:
                asce->val = vcpu->arch.sie_block->gcr[13];
                return 0;
        case PSW_AS_ACCREG:
                rc = ar_translation(vcpu, asce, ar, mode);
                if (rc > 0)
                        return trans_exc(vcpu, rc, ga, ar, mode, PROT_TYPE_ALC);
                return rc;
        }
        return 0;
}

static int deref_table(struct kvm *kvm, unsigned long gpa, unsigned long *val)
{
        return kvm_read_guest(kvm, gpa, val, sizeof(*val));
}

/**
 * guest_translate - translate a guest virtual into a guest absolute address
 * @vcpu: virtual cpu
 * @gva: guest virtual address
 * @gpa: points to where guest physical (absolute) address should be stored
 * @asce: effective asce
 * @mode: indicates the access mode to be used
 *
 * Translate a guest virtual address into a guest absolute address by means
 * of dynamic address translation as specified by the architecture.
 * If the resulting absolute address is not available in the configuration
 * an addressing exception is indicated and @gpa will not be changed.
 *
 * Returns: - zero on success; @gpa contains the resulting absolute address
 *          - a negative value if guest access failed due to e.g. broken
 *            guest mapping
 *          - a positve value if an access exception happened. In this case
 *            the returned value is the program interruption code as defined
 *            by the architecture
 */
static unsigned long guest_translate(struct kvm_vcpu *vcpu, unsigned long gva,
                                     unsigned long *gpa, const union asce asce,
                                     enum gacc_mode mode)
{
        union vaddress vaddr = {.addr = gva};
        union raddress raddr = {.addr = gva};
        union page_table_entry pte;
        int dat_protection = 0;
        union ctlreg0 ctlreg0;
        unsigned long ptr;
        int edat1, edat2;

        ctlreg0.val = vcpu->arch.sie_block->gcr[0];
        edat1 = ctlreg0.edat && test_kvm_facility(vcpu->kvm, 8);
        edat2 = edat1 && test_kvm_facility(vcpu->kvm, 78);
        if (asce.r)
                goto real_address;
        ptr = asce.origin * 4096;
        switch (asce.dt) {
        case ASCE_TYPE_REGION1:
                if (vaddr.rfx01 > asce.tl)
                        return PGM_REGION_FIRST_TRANS;
                ptr += vaddr.rfx * 8;
                break;
        case ASCE_TYPE_REGION2:
                if (vaddr.rfx)
                        return PGM_ASCE_TYPE;
                if (vaddr.rsx01 > asce.tl)
                        return PGM_REGION_SECOND_TRANS;
                ptr += vaddr.rsx * 8;
                break;
        case ASCE_TYPE_REGION3:
                if (vaddr.rfx || vaddr.rsx)
                        return PGM_ASCE_TYPE;
                if (vaddr.rtx01 > asce.tl)
                        return PGM_REGION_THIRD_TRANS;
                ptr += vaddr.rtx * 8;
                break;
        case ASCE_TYPE_SEGMENT:
                if (vaddr.rfx || vaddr.rsx || vaddr.rtx)
                        return PGM_ASCE_TYPE;
                if (vaddr.sx01 > asce.tl)
                        return PGM_SEGMENT_TRANSLATION;
                ptr += vaddr.sx * 8;
                break;
        }
        switch (asce.dt) {
        case ASCE_TYPE_REGION1: {
                union region1_table_entry rfte;

                if (kvm_is_error_gpa(vcpu->kvm, ptr))
                        return PGM_ADDRESSING;
                if (deref_table(vcpu->kvm, ptr, &rfte.val))
                        return -EFAULT;
                if (rfte.i)
                        return PGM_REGION_FIRST_TRANS;
                if (rfte.tt != TABLE_TYPE_REGION1)
                        return PGM_TRANSLATION_SPEC;
                if (vaddr.rsx01 < rfte.tf || vaddr.rsx01 > rfte.tl)
                        return PGM_REGION_SECOND_TRANS;
                if (edat1)
                        dat_protection |= rfte.p;
                ptr = rfte.rto * 4096 + vaddr.rsx * 8;
        }
                /* fallthrough */
        case ASCE_TYPE_REGION2: {
                union region2_table_entry rste;

                if (kvm_is_error_gpa(vcpu->kvm, ptr))
                        return PGM_ADDRESSING;
                if (deref_table(vcpu->kvm, ptr, &rste.val))
                        return -EFAULT;
                if (rste.i)
                        return PGM_REGION_SECOND_TRANS;
                if (rste.tt != TABLE_TYPE_REGION2)
                        return PGM_TRANSLATION_SPEC;
                if (vaddr.rtx01 < rste.tf || vaddr.rtx01 > rste.tl)
                        return PGM_REGION_THIRD_TRANS;
                if (edat1)
                        dat_protection |= rste.p;
                ptr = rste.rto * 4096 + vaddr.rtx * 8;
        }
                /* fallthrough */
        case ASCE_TYPE_REGION3: {
                union region3_table_entry rtte;

                if (kvm_is_error_gpa(vcpu->kvm, ptr))
                        return PGM_ADDRESSING;
                if (deref_table(vcpu->kvm, ptr, &rtte.val))
                        return -EFAULT;
                if (rtte.i)
                        return PGM_REGION_THIRD_TRANS;
                if (rtte.tt != TABLE_TYPE_REGION3)
                        return PGM_TRANSLATION_SPEC;
                if (rtte.cr && asce.p && edat2)
                        return PGM_TRANSLATION_SPEC;
                if (rtte.fc && edat2) {
                        dat_protection |= rtte.fc1.p;
                        raddr.rfaa = rtte.fc1.rfaa;
                        goto absolute_address;
                }
                if (vaddr.sx01 < rtte.fc0.tf)
                        return PGM_SEGMENT_TRANSLATION;
                if (vaddr.sx01 > rtte.fc0.tl)
                        return PGM_SEGMENT_TRANSLATION;
                if (edat1)
                        dat_protection |= rtte.fc0.p;
                ptr = rtte.fc0.sto * 4096 + vaddr.sx * 8;
        }
                /* fallthrough */
        case ASCE_TYPE_SEGMENT: {
                union segment_table_entry ste;

                if (kvm_is_error_gpa(vcpu->kvm, ptr))
                        return PGM_ADDRESSING;
                if (deref_table(vcpu->kvm, ptr, &ste.val))
                        return -EFAULT;
                if (ste.i)
                        return PGM_SEGMENT_TRANSLATION;
                if (ste.tt != TABLE_TYPE_SEGMENT)
                        return PGM_TRANSLATION_SPEC;
                if (ste.cs && asce.p)
                        return PGM_TRANSLATION_SPEC;
                if (ste.fc && edat1) {
                        dat_protection |= ste.fc1.p;
                        raddr.sfaa = ste.fc1.sfaa;
                        goto absolute_address;
                }
                dat_protection |= ste.fc0.p;
                ptr = ste.fc0.pto * 2048 + vaddr.px * 8;
        }
        }
        if (kvm_is_error_gpa(vcpu->kvm, ptr))
                return PGM_ADDRESSING;
        if (deref_table(vcpu->kvm, ptr, &pte.val))
                return -EFAULT;
        if (pte.i)
                return PGM_PAGE_TRANSLATION;
        if (pte.z)
                return PGM_TRANSLATION_SPEC;
        if (pte.co && !edat1)
                return PGM_TRANSLATION_SPEC;
        dat_protection |= pte.p;
        raddr.pfra = pte.pfra;
real_address:
        raddr.addr = kvm_s390_real_to_abs(vcpu, raddr.addr);
absolute_address:
        if (mode == GACC_STORE && dat_protection)
                return PGM_PROTECTION;
        if (kvm_is_error_gpa(vcpu->kvm, raddr.addr))
                return PGM_ADDRESSING;
        *gpa = raddr.addr;
        return 0;
}

static inline int is_low_address(unsigned long ga)
{
        /* Check for address ranges 0..511 and 4096..4607 */
        return (ga & ~0x11fful) == 0;
}

static int low_address_protection_enabled(struct kvm_vcpu *vcpu,
                                          const union asce asce)
{
        union ctlreg0 ctlreg0 = {.val = vcpu->arch.sie_block->gcr[0]};
        psw_t *psw = &vcpu->arch.sie_block->gpsw;

        if (!ctlreg0.lap)
                return 0;
        if (psw_bits(*psw).t && asce.p)
                return 0;
        return 1;
}

static int guest_page_range(struct kvm_vcpu *vcpu, unsigned long ga, ar_t ar,
                            unsigned long *pages, unsigned long nr_pages,
                            const union asce asce, enum gacc_mode mode)
{
        psw_t *psw = &vcpu->arch.sie_block->gpsw;
        int lap_enabled, rc = 0;

        lap_enabled = low_address_protection_enabled(vcpu, asce);
        while (nr_pages) {
                ga = kvm_s390_logical_to_effective(vcpu, ga);
                if (mode == GACC_STORE && lap_enabled && is_low_address(ga))
                        return trans_exc(vcpu, PGM_PROTECTION, ga, ar, mode,
                                         PROT_TYPE_LA);
                ga &= PAGE_MASK;
                if (psw_bits(*psw).t) {
                        rc = guest_translate(vcpu, ga, pages, asce, mode);
                        if (rc < 0)
                                return rc;
                } else {
                        *pages = kvm_s390_real_to_abs(vcpu, ga);
                        if (kvm_is_error_gpa(vcpu->kvm, *pages))
                                rc = PGM_ADDRESSING;
                }
                if (rc)
                        return trans_exc(vcpu, rc, ga, ar, mode, PROT_TYPE_DAT);
                ga += PAGE_SIZE;
                pages++;
                nr_pages--;
        }
        return 0;
}

int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, ar_t ar, void *data,
                 unsigned long len, enum gacc_mode mode)
{
        psw_t *psw = &vcpu->arch.sie_block->gpsw;
        unsigned long _len, nr_pages, gpa, idx;
        unsigned long pages_array[2];
        unsigned long *pages;
        int need_ipte_lock;
        union asce asce;
        int rc;

        if (!len)
                return 0;
        ga = kvm_s390_logical_to_effective(vcpu, ga);
        rc = get_vcpu_asce(vcpu, &asce, ga, ar, mode);
        if (rc)
                return rc;
        nr_pages = (((ga & ~PAGE_MASK) + len - 1) >> PAGE_SHIFT) + 1;
        pages = pages_array;
        if (nr_pages > ARRAY_SIZE(pages_array))
                pages = vmalloc(nr_pages * sizeof(unsigned long));
        if (!pages)
                return -ENOMEM;
        need_ipte_lock = psw_bits(*psw).t && !asce.r;
        if (need_ipte_lock)
                ipte_lock(vcpu);
        rc = guest_page_range(vcpu, ga, ar, pages, nr_pages, asce, mode);
        for (idx = 0; idx < nr_pages && !rc; idx++) {
                gpa = *(pages + idx) + (ga & ~PAGE_MASK);
                _len = min(PAGE_SIZE - (gpa & ~PAGE_MASK), len);
                if (mode == GACC_STORE)
                        rc = kvm_write_guest(vcpu->kvm, gpa, data, _len);
                else
                        rc = kvm_read_guest(vcpu->kvm, gpa, data, _len);
                len -= _len;
                ga += _len;
                data += _len;
        }
        if (need_ipte_lock)
                ipte_unlock(vcpu);
        if (nr_pages > ARRAY_SIZE(pages_array))
                vfree(pages);
        return rc;
}

int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
                      void *data, unsigned long len, enum gacc_mode mode)
{
        unsigned long _len, gpa;
        int rc = 0;

        while (len && !rc) {
                gpa = kvm_s390_real_to_abs(vcpu, gra);
                _len = min(PAGE_SIZE - (gpa & ~PAGE_MASK), len);
                if (mode)
                        rc = write_guest_abs(vcpu, gpa, data, _len);
                else
                        rc = read_guest_abs(vcpu, gpa, data, _len);
                len -= _len;
                gra += _len;
                data += _len;
        }
        return rc;
}

/**
 * guest_translate_address - translate guest logical into guest absolute address
 *
 * Parameter semantics are the same as the ones from guest_translate.
 * The memory contents at the guest address are not changed.
 *
 * Note: The IPTE lock is not taken during this function, so the caller
 * has to take care of this.
 */
int guest_translate_address(struct kvm_vcpu *vcpu, unsigned long gva, ar_t ar,
                            unsigned long *gpa, enum gacc_mode mode)
{
        psw_t *psw = &vcpu->arch.sie_block->gpsw;
        union asce asce;
        int rc;

        gva = kvm_s390_logical_to_effective(vcpu, gva);
        rc = get_vcpu_asce(vcpu, &asce, gva, ar, mode);
        if (rc)
                return rc;
        if (is_low_address(gva) && low_address_protection_enabled(vcpu, asce)) {
                if (mode == GACC_STORE)
                        return trans_exc(vcpu, PGM_PROTECTION, gva, 0,
                                         mode, PROT_TYPE_LA);
        }

        if (psw_bits(*psw).t && !asce.r) {      /* Use DAT? */
                rc = guest_translate(vcpu, gva, gpa, asce, mode);
                if (rc > 0)
                        return trans_exc(vcpu, rc, gva, 0, mode, PROT_TYPE_DAT);
        } else {
                *gpa = kvm_s390_real_to_abs(vcpu, gva);
                if (kvm_is_error_gpa(vcpu->kvm, *gpa))
                        return trans_exc(vcpu, rc, gva, PGM_ADDRESSING, mode, 0);
        }

        return rc;
}

/**
 * check_gva_range - test a range of guest virtual addresses for accessibility
 */
int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva, ar_t ar,
                    unsigned long length, enum gacc_mode mode)
{
        unsigned long gpa;
        unsigned long currlen;
        int rc = 0;

        ipte_lock(vcpu);
        while (length > 0 && !rc) {
                currlen = min(length, PAGE_SIZE - (gva % PAGE_SIZE));
                rc = guest_translate_address(vcpu, gva, ar, &gpa, mode);
                gva += currlen;
                length -= currlen;
        }
        ipte_unlock(vcpu);

        return rc;
}

/**
 * kvm_s390_check_low_addr_prot_real - check for low-address protection
 * @gra: Guest real address
 *
 * Checks whether an address is subject to low-address protection and set
 * up vcpu->arch.pgm accordingly if necessary.
 *
 * Return: 0 if no protection exception, or PGM_PROTECTION if protected.
 */
int kvm_s390_check_low_addr_prot_real(struct kvm_vcpu *vcpu, unsigned long gra)
{
        union ctlreg0 ctlreg0 = {.val = vcpu->arch.sie_block->gcr[0]};

        if (!ctlreg0.lap || !is_low_address(gra))
                return 0;
        return trans_exc(vcpu, PGM_PROTECTION, gra, 0, GACC_STORE, PROT_TYPE_LA);
}

/**
 * kvm_s390_shadow_tables - walk the guest page table and create shadow tables
 * @sg: pointer to the shadow guest address space structure
 * @saddr: faulting address in the shadow gmap
 * @pgt: pointer to the page table address result
 * @fake: pgt references contiguous guest memory block, not a pgtable
 */
static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
                                  unsigned long *pgt, int *dat_protection,
                                  int *fake)
{
        struct gmap *parent;
        union asce asce;
        union vaddress vaddr;
        unsigned long ptr;
        int rc;

        *fake = 0;
        *dat_protection = 0;
        parent = sg->parent;
        vaddr.addr = saddr;
        asce.val = sg->orig_asce;
        ptr = asce.origin * 4096;
        if (asce.r) {
                *fake = 1;
                asce.dt = ASCE_TYPE_REGION1;
        }
        switch (asce.dt) {
        case ASCE_TYPE_REGION1:
                if (vaddr.rfx01 > asce.tl && !asce.r)
                        return PGM_REGION_FIRST_TRANS;
                break;
        case ASCE_TYPE_REGION2:
                if (vaddr.rfx)
                        return PGM_ASCE_TYPE;
                if (vaddr.rsx01 > asce.tl)
                        return PGM_REGION_SECOND_TRANS;
                break;
        case ASCE_TYPE_REGION3:
                if (vaddr.rfx || vaddr.rsx)
                        return PGM_ASCE_TYPE;
                if (vaddr.rtx01 > asce.tl)
                        return PGM_REGION_THIRD_TRANS;
                break;
        case ASCE_TYPE_SEGMENT:
                if (vaddr.rfx || vaddr.rsx || vaddr.rtx)
                        return PGM_ASCE_TYPE;
                if (vaddr.sx01 > asce.tl)
                        return PGM_SEGMENT_TRANSLATION;
                break;
        }

        switch (asce.dt) {
        case ASCE_TYPE_REGION1: {
                union region1_table_entry rfte;

                if (*fake) {
                        /* offset in 16EB guest memory block */
                        ptr = ptr + ((unsigned long) vaddr.rsx << 53UL);
                        rfte.val = ptr;
                        goto shadow_r2t;
                }
                rc = gmap_read_table(parent, ptr + vaddr.rfx * 8, &rfte.val);
                if (rc)
                        return rc;
                if (rfte.i)
                        return PGM_REGION_FIRST_TRANS;
                if (rfte.tt != TABLE_TYPE_REGION1)
                        return PGM_TRANSLATION_SPEC;
                if (vaddr.rsx01 < rfte.tf || vaddr.rsx01 > rfte.tl)
                        return PGM_REGION_SECOND_TRANS;
                if (sg->edat_level >= 1)
                        *dat_protection |= rfte.p;
                ptr = rfte.rto << 12UL;
shadow_r2t:
                rc = gmap_shadow_r2t(sg, saddr, rfte.val, *fake);
                if (rc)
                        return rc;
                /* fallthrough */
        }
        case ASCE_TYPE_REGION2: {
                union region2_table_entry rste;

                if (*fake) {
                        /* offset in 8PB guest memory block */
                        ptr = ptr + ((unsigned long) vaddr.rtx << 42UL);
                        rste.val = ptr;
                        goto shadow_r3t;
                }
                rc = gmap_read_table(parent, ptr + vaddr.rsx * 8, &rste.val);
                if (rc)
                        return rc;
                if (rste.i)
                        return PGM_REGION_SECOND_TRANS;
                if (rste.tt != TABLE_TYPE_REGION2)
                        return PGM_TRANSLATION_SPEC;
                if (vaddr.rtx01 < rste.tf || vaddr.rtx01 > rste.tl)
                        return PGM_REGION_THIRD_TRANS;
                if (sg->edat_level >= 1)
                        *dat_protection |= rste.p;
                ptr = rste.rto << 12UL;
shadow_r3t:
                rste.p |= *dat_protection;
                rc = gmap_shadow_r3t(sg, saddr, rste.val, *fake);
                if (rc)
                        return rc;
                /* fallthrough */
        }
        case ASCE_TYPE_REGION3: {
                union region3_table_entry rtte;

                if (*fake) {
                        /* offset in 4TB guest memory block */
                        ptr = ptr + ((unsigned long) vaddr.sx << 31UL);
                        rtte.val = ptr;
                        goto shadow_sgt;
                }
                rc = gmap_read_table(parent, ptr + vaddr.rtx * 8, &rtte.val);
                if (rc)
                        return rc;
                if (rtte.i)
                        return PGM_REGION_THIRD_TRANS;
                if (rtte.tt != TABLE_TYPE_REGION3)
                        return PGM_TRANSLATION_SPEC;
                if (rtte.cr && asce.p && sg->edat_level >= 2)
                        return PGM_TRANSLATION_SPEC;
                if (rtte.fc && sg->edat_level >= 2) {
                        *dat_protection |= rtte.fc0.p;
                        *fake = 1;
                        ptr = rtte.fc1.rfaa << 31UL;
                        rtte.val = ptr;
                        goto shadow_sgt;
                }
                if (vaddr.sx01 < rtte.fc0.tf || vaddr.sx01 > rtte.fc0.tl)
                        return PGM_SEGMENT_TRANSLATION;
                if (sg->edat_level >= 1)
                        *dat_protection |= rtte.fc0.p;
                ptr = rtte.fc0.sto << 12UL;
shadow_sgt:
                rtte.fc0.p |= *dat_protection;
                rc = gmap_shadow_sgt(sg, saddr, rtte.val, *fake);
                if (rc)
                        return rc;
                /* fallthrough */
        }
        case ASCE_TYPE_SEGMENT: {
                union segment_table_entry ste;

                if (*fake) {
                        /* offset in 2G guest memory block */
                        ptr = ptr + ((unsigned long) vaddr.sx << 20UL);
                        ste.val = ptr;
                        goto shadow_pgt;
                }
                rc = gmap_read_table(parent, ptr + vaddr.sx * 8, &ste.val);
                if (rc)
                        return rc;
                if (ste.i)
                        return PGM_SEGMENT_TRANSLATION;
                if (ste.tt != TABLE_TYPE_SEGMENT)
                        return PGM_TRANSLATION_SPEC;
                if (ste.cs && asce.p)
                        return PGM_TRANSLATION_SPEC;
                *dat_protection |= ste.fc0.p;
                if (ste.fc && sg->edat_level >= 1) {
                        *fake = 1;
                        ptr = ste.fc1.sfaa << 20UL;
                        ste.val = ptr;
                        goto shadow_pgt;
                }
                ptr = ste.fc0.pto << 11UL;
shadow_pgt:
                ste.fc0.p |= *dat_protection;
                rc = gmap_shadow_pgt(sg, saddr, ste.val, *fake);
                if (rc)
                        return rc;
        }
        }
        /* Return the parent address of the page table */
        *pgt = ptr;
        return 0;
}

/**
 * kvm_s390_shadow_fault - handle fault on a shadow page table
 * @vcpu: virtual cpu
 * @sg: pointer to the shadow guest address space structure
 * @saddr: faulting address in the shadow gmap
 *
 * Returns: - 0 if the shadow fault was successfully resolved
 *          - > 0 (pgm exception code) on exceptions while faulting
 *          - -EAGAIN if the caller can retry immediately
 *          - -EFAULT when accessing invalid guest addresses
 *          - -ENOMEM if out of memory
 */
int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *sg,
                          unsigned long saddr)
{
        union vaddress vaddr;
        union page_table_entry pte;
        unsigned long pgt;
        int dat_protection, fake;
        int rc;

        down_read(&sg->mm->mmap_sem);
        /*
         * We don't want any guest-2 tables to change - so the parent
         * tables/pointers we read stay valid - unshadowing is however
         * always possible - only guest_table_lock protects us.
         */
        ipte_lock(vcpu);

        rc = gmap_shadow_pgt_lookup(sg, saddr, &pgt, &dat_protection, &fake);
        if (rc)
                rc = kvm_s390_shadow_tables(sg, saddr, &pgt, &dat_protection,
                                            &fake);

        vaddr.addr = saddr;
        if (fake) {
                /* offset in 1MB guest memory block */
                pte.val = pgt + ((unsigned long) vaddr.px << 12UL);
                goto shadow_page;
        }
        if (!rc)
                rc = gmap_read_table(sg->parent, pgt + vaddr.px * 8, &pte.val);
        if (!rc && pte.i)
                rc = PGM_PAGE_TRANSLATION;
        if (!rc && (pte.z || (pte.co && sg->edat_level < 1)))
                rc = PGM_TRANSLATION_SPEC;
shadow_page:
        pte.p |= dat_protection;
        if (!rc)
                rc = gmap_shadow_page(sg, saddr, __pte(pte.val));
        ipte_unlock(vcpu);
        up_read(&sg->mm->mmap_sem);
        return rc;
}