// SPDX-License-Identifier: GPL-2.0
/*
 * handling diagnose instructions
 *
 * Copyright IBM Corp. 2008, 2020
 *
 *    Author(s): Carsten Otte <cotte@de.ibm.com>
 *               Christian Borntraeger <borntraeger@de.ibm.com>
 */

#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <asm/gmap.h>
#include <asm/virtio-ccw.h>
#include "kvm-s390.h"
#include "trace.h"
#include "trace-s390.h"
#include "gaccess.h"

static int diag_release_pages(struct kvm_vcpu *vcpu)
{
        unsigned long start, end;
        unsigned long prefix  = kvm_s390_get_prefix(vcpu);

        start = vcpu->run->s.regs.gprs[(vcpu->arch.sie_block->ipa & 0xf0) >> 4];
        end = vcpu->run->s.regs.gprs[vcpu->arch.sie_block->ipa & 0xf] + PAGE_SIZE;
        vcpu->stat.instruction_diagnose_10++;

        if (start & ~PAGE_MASK || end & ~PAGE_MASK || start >= end
            || start < 2 * PAGE_SIZE)
                return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);

        VCPU_EVENT(vcpu, 5, "diag release pages %lX %lX", start, end);

        /*
         * We checked for start >= end above, so lets check for the
         * fast path (no prefix swap page involved)
         */
        if (end <= prefix || start >= prefix + 2 * PAGE_SIZE) {
                gmap_discard(vcpu->arch.gmap, start, end);
        } else {
                /*
                 * This is slow path.  gmap_discard will check for start
                 * so lets split this into before prefix, prefix, after
                 * prefix and let gmap_discard make some of these calls
                 * NOPs.
                 */
                gmap_discard(vcpu->arch.gmap, start, prefix);
                if (start <= prefix)
                        gmap_discard(vcpu->arch.gmap, 0, PAGE_SIZE);
                if (end > prefix + PAGE_SIZE)
                        gmap_discard(vcpu->arch.gmap, PAGE_SIZE, 2 * PAGE_SIZE);
                gmap_discard(vcpu->arch.gmap, prefix + 2 * PAGE_SIZE, end);
        }
        return 0;
}

static int __diag_page_ref_service(struct kvm_vcpu *vcpu)
{
        struct prs_parm {
                u16 code;
                u16 subcode;
                u16 parm_len;
                u16 parm_version;
                u64 token_addr;
                u64 select_mask;
                u64 compare_mask;
                u64 zarch;
        };
        struct prs_parm parm;
        int rc;
        u16 rx = (vcpu->arch.sie_block->ipa & 0xf0) >> 4;
        u16 ry = (vcpu->arch.sie_block->ipa & 0x0f);

        VCPU_EVENT(vcpu, 3, "diag page reference parameter block at 0x%llx",
                   vcpu->run->s.regs.gprs[rx]);
        vcpu->stat.instruction_diagnose_258++;
        if (vcpu->run->s.regs.gprs[rx] & 7)
                return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
        rc = read_guest(vcpu, vcpu->run->s.regs.gprs[rx], rx, &parm, sizeof(parm));
        if (rc)
                return kvm_s390_inject_prog_cond(vcpu, rc);
        if (parm.parm_version != 2 || parm.parm_len < 5 || parm.code != 0x258)
                return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);

        switch (parm.subcode) {
        case 0: /* TOKEN */
                VCPU_EVENT(vcpu, 3, "pageref token addr 0x%llx "
                           "select mask 0x%llx compare mask 0x%llx",
                           parm.token_addr, parm.select_mask, parm.compare_mask);
                if (vcpu->arch.pfault_token != KVM_S390_PFAULT_TOKEN_INVALID) {
                        /*
                         * If the pagefault handshake is already activated,
                         * the token must not be changed.  We have to return
                         * decimal 8 instead, as mandated in SC24-6084.
                         */
                        vcpu->run->s.regs.gprs[ry] = 8;
                        return 0;
                }

                if ((parm.compare_mask & parm.select_mask) != parm.compare_mask ||
                    parm.token_addr & 7 || parm.zarch != 0x8000000000000000ULL)
                        return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);

                if (kvm_is_error_gpa(vcpu->kvm, parm.token_addr))
                        return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);

                vcpu->arch.pfault_token = parm.token_addr;
                vcpu->arch.pfault_select = parm.select_mask;
                vcpu->arch.pfault_compare = parm.compare_mask;
                vcpu->run->s.regs.gprs[ry] = 0;
                rc = 0;
                break;
        case 1: /*
                 * CANCEL
                 * Specification allows to let already pending tokens survive
                 * the cancel, therefore to reduce code complexity, we assume
                 * all outstanding tokens are already pending.
                 */
                VCPU_EVENT(vcpu, 3, "pageref cancel addr 0x%llx", parm.token_addr);
                if (parm.token_addr || parm.select_mask ||
                    parm.compare_mask || parm.zarch)
                        return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);

                vcpu->run->s.regs.gprs[ry] = 0;
                /*
                 * If the pfault handling was not established or is already
                 * canceled SC24-6084 requests to return decimal 4.
                 */
                if (vcpu->arch.pfault_token == KVM_S390_PFAULT_TOKEN_INVALID)
                        vcpu->run->s.regs.gprs[ry] = 4;
                else
                        vcpu->arch.pfault_token = KVM_S390_PFAULT_TOKEN_INVALID;

                rc = 0;
                break;
        default:
                rc = -EOPNOTSUPP;
                break;
        }

        return rc;
}

static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
{
        VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
        vcpu->stat.instruction_diagnose_44++;
        kvm_vcpu_on_spin(vcpu, true);
        return 0;
}

static int forward_cnt;
static unsigned long cur_slice;

static int diag9c_forwarding_overrun(void)
{
        /* Reset the count on a new slice */
        if (time_after(jiffies, cur_slice)) {
                cur_slice = jiffies;
                forward_cnt = diag9c_forwarding_hz / HZ;
        }
        return forward_cnt-- <= 0 ? 1 : 0;
}

static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu)
{
        struct kvm_vcpu *tcpu;
        int tid;

        tid = vcpu->run->s.regs.gprs[(vcpu->arch.sie_block->ipa & 0xf0) >> 4];
        vcpu->stat.instruction_diagnose_9c++;

        /* yield to self */
        if (tid == vcpu->vcpu_id)
                goto no_yield;

        /* yield to invalid */
        tcpu = kvm_get_vcpu_by_id(vcpu->kvm, tid);
        if (!tcpu)
                goto no_yield;

        /* target guest VCPU already running */
        if (READ_ONCE(tcpu->cpu) >= 0) {
                if (!diag9c_forwarding_hz || diag9c_forwarding_overrun())
                        goto no_yield;

                /* target host CPU already running */
                if (!vcpu_is_preempted(tcpu->cpu))
                        goto no_yield;
                smp_yield_cpu(tcpu->cpu);
                VCPU_EVENT(vcpu, 5,
                           "diag time slice end directed to %d: yield forwarded",
                           tid);
                vcpu->stat.diag_9c_forward++;
                return 0;
        }

        if (kvm_vcpu_yield_to(tcpu) <= 0)
                goto no_yield;

        VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d: done", tid);
        return 0;
no_yield:
        VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d: ignored", tid);
        vcpu->stat.diag_9c_ignored++;
        return 0;
}

static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
{
        unsigned int reg = vcpu->arch.sie_block->ipa & 0xf;
        unsigned long subcode = vcpu->run->s.regs.gprs[reg] & 0xffff;

        VCPU_EVENT(vcpu, 3, "diag ipl functions, subcode %lx", subcode);
        vcpu->stat.instruction_diagnose_308++;
        switch (subcode) {
        case 3:
                vcpu->run->s390_reset_flags = KVM_S390_RESET_CLEAR;
                break;
        case 4:
                vcpu->run->s390_reset_flags = 0;
                break;
        default:
                return -EOPNOTSUPP;
        }

        /*
         * no need to check the return value of vcpu_stop as it can only have
         * an error for protvirt, but protvirt means user cpu state
         */
        if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm))
                kvm_s390_vcpu_stop(vcpu);
        vcpu->run->s390_reset_flags |= KVM_S390_RESET_SUBSYSTEM;
        vcpu->run->s390_reset_flags |= KVM_S390_RESET_IPL;
        vcpu->run->s390_reset_flags |= KVM_S390_RESET_CPU_INIT;
        vcpu->run->exit_reason = KVM_EXIT_S390_RESET;
        VCPU_EVENT(vcpu, 3, "requesting userspace resets %llx",
          vcpu->run->s390_reset_flags);
        trace_kvm_s390_request_resets(vcpu->run->s390_reset_flags);
        return -EREMOTE;
}

static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu)
{
        int ret;

        vcpu->stat.instruction_diagnose_500++;
        /* No virtio-ccw notification? Get out quickly. */
        if (!vcpu->kvm->arch.css_support ||
            (vcpu->run->s.regs.gprs[1] != KVM_S390_VIRTIO_CCW_NOTIFY))
                return -EOPNOTSUPP;

        VCPU_EVENT(vcpu, 4, "diag 0x500 schid 0x%8.8x queue 0x%x cookie 0x%llx",
                            (u32) vcpu->run->s.regs.gprs[2],
                            (u32) vcpu->run->s.regs.gprs[3],
                            vcpu->run->s.regs.gprs[4]);

        /*
         * The layout is as follows:
         * - gpr 2 contains the subchannel id (passed as addr)
         * - gpr 3 contains the virtqueue index (passed as datamatch)
         * - gpr 4 contains the index on the bus (optionally)
         */
        ret = kvm_io_bus_write_cookie(vcpu, KVM_VIRTIO_CCW_NOTIFY_BUS,
                                      vcpu->run->s.regs.gprs[2] & 0xffffffff,
                                      8, &vcpu->run->s.regs.gprs[3],
                                      vcpu->run->s.regs.gprs[4]);

        /*
         * Return cookie in gpr 2, but don't overwrite the register if the
         * diagnose will be handled by userspace.
         */
        if (ret != -EOPNOTSUPP)
                vcpu->run->s.regs.gprs[2] = ret;
        /* kvm_io_bus_write_cookie returns -EOPNOTSUPP if it found no match. */
        return ret < 0 ? ret : 0;
}

int kvm_s390_handle_diag(struct kvm_vcpu *vcpu)
{
        int code = kvm_s390_get_base_disp_rs(vcpu, NULL) & 0xffff;

        if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
                return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);

        trace_kvm_s390_handle_diag(vcpu, code);
        switch (code) {
        case 0x10:
                return diag_release_pages(vcpu);
        case 0x44:
                return __diag_time_slice_end(vcpu);
        case 0x9c:
                return __diag_time_slice_end_directed(vcpu);
        case 0x258:
                return __diag_page_ref_service(vcpu);
        case 0x308:
                return __diag_ipl_functions(vcpu);
        case 0x500:
                return __diag_virtio_hypercall(vcpu);
        default:
                vcpu->stat.instruction_diagnose_other++;
                return -EOPNOTSUPP;
        }
}