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Revert "svm: Fix AVIC incomplete IPI emulation"

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commit 4a58038b9e upstream.

This reverts commit bb218fbcfa.

As Oren Twaig pointed out the old discussion:

  https://patchwork.kernel.org/patch/8292231/

that the change coud potentially cause an extra IPI to be sent to
the destination vcpu because the AVIC hardware already set the IRR bit
before the incomplete IPI #VMEXIT with id=1 (target vcpu is not running).
Since writting to ICR and ICR2 will also set the IRR. If something triggers
the destination vcpu to get scheduled before the emulation finishes, then
this could result in an additional IPI.

Also, the issue mentioned in the commit bb218fbcfa was misdiagnosed.

Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reported-by: Oren Twaig <oren@scalemp.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Suthikulpanit, Suravee
2019-03-20 08:12:28 +00:00
committed by Greg Kroah-Hartman
parent bc6b83db8f
commit c197e4693a
1 changed files with 15 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
arch/x86/kvm/svm.c
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@@ -4017,14 +4017,25 @@ static int avic_incomplete_ipi_interception(struct vcpu_svm *svm)
kvm_lapic_reg_write(apic, APIC_ICR, icrl);
break;
case AVIC_IPI_FAILURE_TARGET_NOT_RUNNING: {
int i;
struct kvm_vcpu *vcpu;
struct kvm *kvm = svm->vcpu.kvm;
struct kvm_lapic *apic = svm->vcpu.arch.apic;
/*
* Update ICR high and low, then emulate sending IPI,
* which is handled when writing APIC_ICR.
* At this point, we expect that the AVIC HW has already
* set the appropriate IRR bits on the valid target
* vcpus. So, we just need to kick the appropriate vcpu.
*/
kvm_lapic_reg_write(apic, APIC_ICR2, icrh);
kvm_lapic_reg_write(apic, APIC_ICR, icrl);
kvm_for_each_vcpu(i, vcpu, kvm) {
bool m = kvm_apic_match_dest(vcpu, apic,
icrl & KVM_APIC_SHORT_MASK,
GET_APIC_DEST_FIELD(icrh),
icrl & KVM_APIC_DEST_MASK);
if (m && !avic_vcpu_is_running(vcpu))
kvm_vcpu_wake_up(vcpu);
}
break;
}
case AVIC_IPI_FAILURE_INVALID_TARGET: