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

#include <linux/vmalloc.h>
#include <linux/err.h>
#include <asm/pgtable.h>
#include "kvm-s390.h"
#include "gaccess.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 */
};


int ipte_lock_held(struct kvm_vcpu *vcpu)
{
        union ipte_control *ic = &vcpu->kvm->arch.sca->ipte_control;

        if (vcpu->arch.sie_block->eca & 1)
                return ic->kh != 0;
        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;
        ic = &vcpu->kvm->arch.sca->ipte_control;
        do {
                old = READ_ONCE(*ic);
                while (old.k) {
                        cond_resched();
                        old = READ_ONCE(*ic);
                }
                new = old;
                new.k = 1;
        } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
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;
        ic = &vcpu->kvm->arch.sca->ipte_control;
        do {
                old = READ_ONCE(*ic);
                new = old;
                new.k = 0;
        } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
        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;

        ic = &vcpu->kvm->arch.sca->ipte_control;
        do {
                old = READ_ONCE(*ic);
                while (old.kg) {
                        cond_resched();
                        old = READ_ONCE(*ic);
                }
                new = old;
                new.k = 1;
                new.kh++;
        } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
}

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

        ic = &vcpu->kvm->arch.sca->ipte_control;
        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);
        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 unsigned long get_vcpu_asce(struct kvm_vcpu *vcpu)
{
        switch (psw_bits(vcpu->arch.sie_block->gpsw).as) {
        case PSW_AS_PRIMARY:
                return vcpu->arch.sie_block->gcr[1];
        case PSW_AS_SECONDARY:
                return vcpu->arch.sie_block->gcr[7];
        case PSW_AS_HOME:
                return vcpu->arch.sie_block->gcr[13];
        }
        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
 * @write: indicates if access is a write access
 *
 * Translate a guest virtual address into a guest absolute address by means
 * of dynamic address translation as specified by the architecuture.
 * 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, int write)
{
        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;
        union asce asce;

        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);
        asce.val = get_vcpu_asce(vcpu);
        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 (write && 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)
{
        union ctlreg0 ctlreg0 = {.val = vcpu->arch.sie_block->gcr[0]};
        psw_t *psw = &vcpu->arch.sie_block->gpsw;
        union asce asce;

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

struct trans_exc_code_bits {
        unsigned long addr : 52; /* Translation-exception Address */
        unsigned long fsi  : 2;  /* Access Exception Fetch/Store Indication */
        unsigned long      : 7;
        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 */
};

static int guest_page_range(struct kvm_vcpu *vcpu, unsigned long ga,
                            unsigned long *pages, unsigned long nr_pages,
                            int write)
{
        struct kvm_s390_pgm_info *pgm = &vcpu->arch.pgm;
        psw_t *psw = &vcpu->arch.sie_block->gpsw;
        struct trans_exc_code_bits *tec_bits;
        int lap_enabled, rc;

        memset(pgm, 0, sizeof(*pgm));
        tec_bits = (struct trans_exc_code_bits *)&pgm->trans_exc_code;
        tec_bits->fsi = write ? FSI_STORE : FSI_FETCH;
        tec_bits->as = psw_bits(*psw).as;
        lap_enabled = low_address_protection_enabled(vcpu);
        while (nr_pages) {
                ga = kvm_s390_logical_to_effective(vcpu, ga);
                tec_bits->addr = ga >> PAGE_SHIFT;
                if (write && lap_enabled && is_low_address(ga)) {
                        pgm->code = PGM_PROTECTION;
                        return pgm->code;
                }
                ga &= PAGE_MASK;
                if (psw_bits(*psw).t) {
                        rc = guest_translate(vcpu, ga, pages, write);
                        if (rc < 0)
                                return rc;
                        if (rc == PGM_PROTECTION)
                                tec_bits->b61 = 1;
                        if (rc)
                                pgm->code = rc;
                } else {
                        *pages = kvm_s390_real_to_abs(vcpu, ga);
                        if (kvm_is_error_gpa(vcpu->kvm, *pages))
                                pgm->code = PGM_ADDRESSING;
                }
                if (pgm->code)
                        return pgm->code;
                ga += PAGE_SIZE;
                pages++;
                nr_pages--;
        }
        return 0;
}

int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, void *data,
                 unsigned long len, int write)
{
        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;
        /* Access register mode is not supported yet. */
        if (psw_bits(*psw).t && psw_bits(*psw).as == PSW_AS_ACCREG)
                return -EOPNOTSUPP;
        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;
        asce.val = get_vcpu_asce(vcpu);
        need_ipte_lock = psw_bits(*psw).t && !asce.r;
        if (need_ipte_lock)
                ipte_lock(vcpu);
        rc = guest_page_range(vcpu, ga, pages, nr_pages, write);
        for (idx = 0; idx < nr_pages && !rc; idx++) {
                gpa = *(pages + idx) + (ga & ~PAGE_MASK);
                _len = min(PAGE_SIZE - (gpa & ~PAGE_MASK), len);
                if (write)
                        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, int write)
{
        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 (write)
                        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,
                            unsigned long *gpa, int write)
{
        struct kvm_s390_pgm_info *pgm = &vcpu->arch.pgm;
        psw_t *psw = &vcpu->arch.sie_block->gpsw;
        struct trans_exc_code_bits *tec;
        union asce asce;
        int rc;

        /* Access register mode is not supported yet. */
        if (psw_bits(*psw).t && psw_bits(*psw).as == PSW_AS_ACCREG)
                return -EOPNOTSUPP;

        gva = kvm_s390_logical_to_effective(vcpu, gva);
        memset(pgm, 0, sizeof(*pgm));
        tec = (struct trans_exc_code_bits *)&pgm->trans_exc_code;
        tec->as = psw_bits(*psw).as;
        tec->fsi = write ? FSI_STORE : FSI_FETCH;
        tec->addr = gva >> PAGE_SHIFT;
        if (is_low_address(gva) && low_address_protection_enabled(vcpu)) {
                if (write) {
                        rc = pgm->code = PGM_PROTECTION;
                        return rc;
                }
        }

        asce.val = get_vcpu_asce(vcpu);
        if (psw_bits(*psw).t && !asce.r) {      /* Use DAT? */
                rc = guest_translate(vcpu, gva, gpa, write);
                if (rc > 0) {
                        if (rc == PGM_PROTECTION)
                                tec->b61 = 1;
                        pgm->code = rc;
                }
        } else {
                rc = 0;
                *gpa = kvm_s390_real_to_abs(vcpu, gva);
                if (kvm_is_error_gpa(vcpu->kvm, *gpa))
                        rc = pgm->code = PGM_ADDRESSING;
        }

        return rc;
}

/**
 * kvm_s390_check_low_addr_protection - check for low-address protection
 * @ga: Guest 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_protection(struct kvm_vcpu *vcpu, unsigned long ga)
{
        struct kvm_s390_pgm_info *pgm = &vcpu->arch.pgm;
        psw_t *psw = &vcpu->arch.sie_block->gpsw;
        struct trans_exc_code_bits *tec_bits;

        if (!is_low_address(ga) || !low_address_protection_enabled(vcpu))
                return 0;

        memset(pgm, 0, sizeof(*pgm));
        tec_bits = (struct trans_exc_code_bits *)&pgm->trans_exc_code;
        tec_bits->fsi = FSI_STORE;
        tec_bits->as = psw_bits(*psw).as;
        tec_bits->addr = ga >> PAGE_SHIFT;
        pgm->code = PGM_PROTECTION;

        return pgm->code;
}