[PATCH 5.14 113/169] KVM: x86: check for interrupts before deciding whether to exit the fast path

Greg Kroah-Hartman
2021-10-25T19:53:43Z

From: Paolo Bonzini <pbonzini@redhat.com>

commit de7cd3f6761f49bef044ec49493d88737a70f1a6 upstream.

The kvm_x86_sync_pir_to_irr callback can sometimes set KVM_REQ_EVENT.
If that happens exactly at the time that an exit is handled as
EXIT_FASTPATH_REENTER_GUEST, vcpu_enter_guest will go incorrectly
through the loop that calls kvm_x86_run, instead of processing
the request promptly.

Fixes: 379a3c8ee444 ("KVM: VMX: Optimize posted-interrupt delivery for timer fastpath")
Cc: stable@vger.kernel.org
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/x86.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9642,14 +9642,14 @@ static int vcpu_enter_guest(struct kvm_v
if (likely(exit_fastpath != EXIT_FASTPATH_REENTER_GUEST))
break;

- if (unlikely(kvm_vcpu_exit_request(vcpu))) {
+ if (vcpu->arch.apicv_active)
+ static_call(kvm_x86_sync_pir_to_irr)(vcpu);
+
+ if (unlikely(kvm_vcpu_exit_request(vcpu))) {
exit_fastpath = EXIT_FASTPATH_EXIT_HANDLED;
break;
}
-
- if (vcpu->arch.apicv_active)
- static_call(kvm_x86_sync_pir_to_irr)(vcpu);
- }
+ }

/*
* Do this here before restoring debug registers on the host. And