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KVM: Never clear KVM_REQ_VM_DEAD from a vCPU's requests

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Use kvm_test_request() instead of kvm_check_request() when querying
KVM_REQ_VM_DEAD, i.e. don't clear KVM_REQ_VM_DEAD, as the entire purpose
of KVM_REQ_VM_DEAD is to prevent the vCPU from enterring the guest ever
again, even if userspace insists on redoing KVM_RUN.

Ensuring KVM_REQ_VM_DEAD is never cleared will allow relaxing KVM's rule
that ioctls can't be invoked on dead VMs, to only disallow ioctls if the
VM is bugged, i.e. if KVM hit a KVM_BUG_ON().

Opportunistically add compile-time assertions to guard against clearing
KVM_REQ_VM_DEAD through the standard APIs.

Reviewed-by: Kai Huang <kai.huang@intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://patch.msgid.link/20260806214618.82180-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-08-06 14:46:18 -07:00
parent f13368e0ac
commit 8cd280282d
5 changed files with 11 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/arm64/kvm/arm.c
View File

@ -1129,7 +1129,7 @@ static int kvm_vcpu_suspend(struct kvm_vcpu *vcpu)
static int check_vcpu_requests(struct kvm_vcpu *vcpu)
{
if (kvm_request_pending(vcpu)) {
if (kvm_check_request(KVM_REQ_VM_DEAD, vcpu))
if (kvm_test_request(KVM_REQ_VM_DEAD, vcpu))
return -EIO;
if (kvm_check_request(KVM_REQ_SLEEP, vcpu))

2
arch/x86/kvm/mmu/mmu.c
View File

@ -5058,7 +5058,7 @@ static int kvm_tdp_page_prefault(struct kvm_vcpu *vcpu, gpa_t gpa,
if (signal_pending(current))
return -EINTR;
if (kvm_check_request(KVM_REQ_VM_DEAD, vcpu))
if (kvm_test_request(KVM_REQ_VM_DEAD, vcpu))
return -EIO;
cond_resched();

2
arch/x86/kvm/vmx/tdx.c
View File

@ -1995,7 +1995,7 @@ static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu)
if (kvm_vcpu_has_events(vcpu) || signal_pending(current))
break;
if (kvm_check_request(KVM_REQ_VM_DEAD, vcpu)) {
if (kvm_test_request(KVM_REQ_VM_DEAD, vcpu)) {
ret = -EIO;
break;
}

2
arch/x86/kvm/x86.c
View File

@ -8060,7 +8060,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
bool req_immediate_exit = false;
if (kvm_request_pending(vcpu)) {
if (kvm_check_request(KVM_REQ_VM_DEAD, vcpu)) {
if (kvm_test_request(KVM_REQ_VM_DEAD, vcpu)) {
r = -EIO;
goto out;
}

9
include/linux/kvm_host.h
View File

@ -2324,13 +2324,18 @@ static inline bool kvm_test_request(int req, struct kvm_vcpu *vcpu)
return test_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests);
}
static inline void kvm_clear_request(int req, struct kvm_vcpu *vcpu)
static __always_inline void kvm_clear_request(int req, struct kvm_vcpu *vcpu)
{
BUILD_BUG_ON(req == KVM_REQ_VM_DEAD);
clear_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests);
}
static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
static __always_inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
{
/* Once a VM is dead, it needs to stay dead. */
BUILD_BUG_ON(req == KVM_REQ_VM_DEAD);
if (kvm_test_request(req, vcpu)) {
kvm_clear_request(req, vcpu);