[PATCH 6.1 034/481] KVM: x86: WARN if a vCPU gets a valid wakeup that KVM cant yet inject

Greg Kroah-Hartman
2026-03-23T15:23:48Z

6.1-stable review patch. If anyone has any objections, please let me know.

------------------

From: Sean Christopherson <seanjc@google.com>

[ Upstream commit 45405155d876c326da89162b8173b8cc9ab7ed75 ]

WARN if a blocking vCPU is awakened by a valid wake event that KVM can't
inject, e.g. because KVM needs to complete a nested VM-enter, or needs to
re-inject an exception. For the nested VM-Enter case, KVM is supposed to
clear "nested_run_pending" if L1 puts L2 into HLT, i.e. entering HLT
"completes" the nested VM-Enter. And for already-injected exceptions, it
should be impossible for the vCPU to be in a blocking state if a VM-Exit
occurred while an exception was being vectored.

Link: https://lore.kernel.org/r/20240607172609.3205077-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Stable-dep-of: ead63640d4e7 ("KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/x86.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b6fdf084fc92a..824844a7c6e88 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11064,7 +11064,10 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu)
* causes a spurious wakeup from HLT).
*/
if (is_guest_mode(vcpu)) {
- if (kvm_check_nested_events(vcpu) < 0)
+ int r = kvm_check_nested_events(vcpu);
+
+ WARN_ON_ONCE(r == -EBUSY);
+ if (r < 0)
return 0;
}

--
2.51.0