Patch "KVM: SVM: Process ICR on AVIC IPI delivery failure due to invalid target" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    KVM: SVM: Process ICR on AVIC IPI delivery failure due to invalid target

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-svm-process-icr-on-avic-ipi-delivery-failure-due.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8f09813101a85e82da8d99e36f941f6bf73e3e05
Author: Sean Christopherson <seanjc@xxxxxxxxxx>
Date:   Fri Jan 6 01:12:37 2023 +0000

    KVM: SVM: Process ICR on AVIC IPI delivery failure due to invalid target
    
    [ Upstream commit 5aede752a839904059c2b5d68be0dc4501c6c15f ]
    
    Emulate ICR writes on AVIC IPI failures due to invalid targets using the
    same logic as failures due to invalid types.  AVIC acceleration fails if
    _any_ of the targets are invalid, and crucially VM-Exits before sending
    IPIs to targets that _are_ valid.  In logical mode, the destination is a
    bitmap, i.e. a single IPI can target multiple logical IDs.  Doing nothing
    causes KVM to drop IPIs if at least one target is valid and at least one
    target is invalid.
    
    Fixes: 18f40c53e10f ("svm: Add VMEXIT handlers for AVIC")
    Cc: stable@xxxxxxxxxxxxxxx
    Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
    Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
    Message-Id: <20230106011306.85230-5-seanjc@xxxxxxxxxx>
    Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 52778be77713f..b595a33860d70 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -318,14 +318,18 @@ int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu)
 	trace_kvm_avic_incomplete_ipi(vcpu->vcpu_id, icrh, icrl, id, index);
 
 	switch (id) {
+	case AVIC_IPI_FAILURE_INVALID_TARGET:
 	case AVIC_IPI_FAILURE_INVALID_INT_TYPE:
 		/*
 		 * Emulate IPIs that are not handled by AVIC hardware, which
-		 * only virtualizes Fixed, Edge-Triggered INTRs.  The exit is
-		 * a trap, e.g. ICR holds the correct value and RIP has been
-		 * advanced, KVM is responsible only for emulating the IPI.
-		 * Sadly, hardware may sometimes leave the BUSY flag set, in
-		 * which case KVM needs to emulate the ICR write as well in
+		 * only virtualizes Fixed, Edge-Triggered INTRs, and falls over
+		 * if _any_ targets are invalid, e.g. if the logical mode mask
+		 * is a superset of running vCPUs.
+		 *
+		 * The exit is a trap, e.g. ICR holds the correct value and RIP
+		 * has been advanced, KVM is responsible only for emulating the
+		 * IPI.  Sadly, hardware may sometimes leave the BUSY flag set,
+		 * in which case KVM needs to emulate the ICR write as well in
 		 * order to clear the BUSY flag.
 		 */
 		if (icrl & APIC_ICR_BUSY)
@@ -341,8 +345,6 @@ int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu)
 		 */
 		avic_kick_target_vcpus(vcpu->kvm, apic, icrl, icrh);
 		break;
-	case AVIC_IPI_FAILURE_INVALID_TARGET:
-		break;
 	case AVIC_IPI_FAILURE_INVALID_BACKING_PAGE:
 		WARN_ONCE(1, "Invalid backing page\n");
 		break;