The patch below does not apply to the 5.15-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.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 97a71c444a147ae41c7d0ab5b3d855d7f762f3ed # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '167812333979118@kroah.com' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

97a71c444a14 ("KVM: x86: Purge "highest ISR" cache when updating APICv state") ce0a58f4756c ("KVM: x86: Move "apicv_active" into "struct kvm_lapic"") d39850f57d21 ("KVM: x86: Drop @vcpu parameter from kvm_x86_ops.hwapic_isr_update()") 47e8eec83262 ("Merge tag 'kvmarm-5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 97a71c444a147ae41c7d0ab5b3d855d7f762f3ed Mon Sep 17 00:00:00 2001 From: Sean Christopherson seanjc@google.com Date: Fri, 6 Jan 2023 01:12:35 +0000 Subject: [PATCH] KVM: x86: Purge "highest ISR" cache when updating APICv state

Purge the "highest ISR" cache when updating APICv state on a vCPU. The cache must not be used when APICv is active as hardware may emulate EOIs (and other operations) without exiting to KVM.

This fixes a bug where KVM will effectively block IRQs in perpetuity due to the "highest ISR" never getting reset if APICv is activated on a vCPU while an IRQ is in-service. Hardware emulates the EOI and KVM never gets a chance to update its cache.

Fixes: b26a695a1d78 ("kvm: lapic: Introduce APICv update helper function") Cc: stable@vger.kernel.org Cc: Suravee Suthikulpanit suravee.suthikulpanit@amd.com Cc: Maxim Levitsky mlevitsk@redhat.com Reviewed-by: Paolo Bonzini pbonzini@redhat.com Reviewed-by: Maxim Levitsky mlevitsk@redhat.com Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20230106011306.85230-3-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 5c0f93fc073a..33a661d82da7 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2424,6 +2424,7 @@ void kvm_apic_update_apicv(struct kvm_vcpu *vcpu) */ apic->isr_count = count_vectors(apic->regs + APIC_ISR); } + apic->highest_isr_cache = -1; }

void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event) @@ -2479,7 +2480,6 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event) kvm_lapic_set_reg(apic, APIC_TMR + 0x10 * i, 0); } kvm_apic_update_apicv(vcpu); - apic->highest_isr_cache = -1; update_divide_count(apic); atomic_set(&apic->lapic_timer.pending, 0);

@@ -2767,7 +2767,6 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s) __start_apic_timer(apic, APIC_TMCCT); kvm_lapic_set_reg(apic, APIC_TMCCT, 0); kvm_apic_update_apicv(vcpu); - apic->highest_isr_cache = -1; if (apic->apicv_active) { static_call_cond(kvm_x86_apicv_post_state_restore)(vcpu); static_call_cond(kvm_x86_hwapic_irr_update)(vcpu, apic_find_highest_irr(apic));