The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From de7cd3f6761f49bef044ec49493d88737a70f1a6 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini pbonzini@redhat.com Date: Wed, 20 Oct 2021 06:27:36 -0400 Subject: [PATCH] KVM: x86: check for interrupts before deciding whether to exit the fast path
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
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0c8b5129effd..381384a54790 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9643,14 +9643,14 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) 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