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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2024 Ventana Micro Systems Inc.
*/
#include <linux/kvm_host.h>
#include <linux/wordpart.h>
#include <asm/kvm_vcpu_sbi.h>
#include <asm/sbi.h>
static int kvm_sbi_ext_susp_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
struct kvm_vcpu_sbi_return *retdata)
{
struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
unsigned long funcid = cp->a6;
unsigned long hva, i;
struct kvm_vcpu *tmp;
switch (funcid) {
case SBI_EXT_SUSP_SYSTEM_SUSPEND:
if (lower_32_bits(cp->a0) != SBI_SUSP_SLEEP_TYPE_SUSPEND_TO_RAM) {
retdata->err_val = SBI_ERR_INVALID_PARAM;
return 0;
}
if (!(cp->sstatus & SR_SPP)) {
retdata->err_val = SBI_ERR_FAILURE;
return 0;
}
hva = kvm_vcpu_gfn_to_hva_prot(vcpu, cp->a1 >> PAGE_SHIFT, NULL);
if (kvm_is_error_hva(hva)) {
retdata->err_val = SBI_ERR_INVALID_ADDRESS;
return 0;
}
/*
* Check that all other vCPUs are stopped before entering
* system suspend.
*
* There is a known TOCTOU race here: a concurrent HSM
* HART_START on another vCPU can start a vCPU after it
* has already passed this check, violating the invariant.
*
* We do not fix this because:
* 1. Triggering the race requires a pathological guest.
* 2. Only guest state is at risk, not host integrity.
* 3. Userspace can double-check vCPU states before
* proceeding with suspend.
*/
kvm_for_each_vcpu(i, tmp, vcpu->kvm) {
if (tmp == vcpu)
continue;
if (!kvm_riscv_vcpu_stopped(tmp)) {
retdata->err_val = SBI_ERR_DENIED;
return 0;
}
}
kvm_riscv_vcpu_sbi_request_reset(vcpu, cp->a1, cp->a2);
/* userspace provides the suspend implementation */
return kvm_riscv_vcpu_sbi_forward_handler(vcpu, run, retdata);
default:
retdata->err_val = SBI_ERR_NOT_SUPPORTED;
break;
}
return 0;
}
const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_susp = {
.extid_start = SBI_EXT_SUSP,
.extid_end = SBI_EXT_SUSP,
.default_disabled = true,
.handler = kvm_sbi_ext_susp_handler,
};
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