On 3/6/2025 9:29 PM, Paolo Bonzini wrote:
KVM_CAP_SYNC_REGS does not make sense for VMs with protected guest state,
since the register values cannot actually be written. Return 0
when using the VM-level KVM_CHECK_EXTENSION ioctl, and accordingly
return -EINVAL from KVM_RUN if the valid/dirty fields are nonzero.
However, on exit from KVM_RUN userspace could have placed a nonzero
value into kvm_run->kvm_valid_regs, so check guest_state_protected
again and skip store_regs() in that case.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reviewed-by: Pankaj Gupta <pankaj.gupta@xxxxxxx>
Also, boot tested a SNP guest on 6.14-rc5 host with the patch applied.
Thanks,
Pankaj
---
arch/x86/kvm/x86.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index aaa067b79095..b416eec5c167 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4586,6 +4586,11 @@ static bool kvm_is_vm_type_supported(unsigned long type)
return type < 32 && (kvm_caps.supported_vm_types & BIT(type));
}
+static inline u32 kvm_sync_valid_fields(struct kvm *kvm)
+{
+ return kvm && kvm->arch.has_protected_state ? 0 : KVM_SYNC_X86_VALID_FIELDS;
+}
+
int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
{
int r = 0;
@@ -4694,7 +4699,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
break;
#endif
case KVM_CAP_SYNC_REGS:
- r = KVM_SYNC_X86_VALID_FIELDS;
+ r = kvm_sync_valid_fields(kvm);
break;
case KVM_CAP_ADJUST_CLOCK:
r = KVM_CLOCK_VALID_FLAGS;
@@ -11503,6 +11508,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
{
struct kvm_queued_exception *ex = &vcpu->arch.exception;
struct kvm_run *kvm_run = vcpu->run;
+ u32 sync_valid_fields;
int r;
r = kvm_mmu_post_init_vm(vcpu->kvm);
@@ -11548,8 +11554,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
goto out;
}
- if ((kvm_run->kvm_valid_regs & ~KVM_SYNC_X86_VALID_FIELDS) ||
- (kvm_run->kvm_dirty_regs & ~KVM_SYNC_X86_VALID_FIELDS)) {
+ sync_valid_fields = kvm_sync_valid_fields(vcpu->kvm);
+ if ((kvm_run->kvm_valid_regs & ~sync_valid_fields) ||
+ (kvm_run->kvm_dirty_regs & ~sync_valid_fields)) {
r = -EINVAL;
goto out;
}
@@ -11607,7 +11614,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
out:
kvm_put_guest_fpu(vcpu);
- if (kvm_run->kvm_valid_regs)
+ if (kvm_run->kvm_valid_regs && likely(!vcpu->arch.guest_state_protected))
store_regs(vcpu);
post_kvm_run_save(vcpu);
kvm_vcpu_srcu_read_unlock(vcpu);
