tree 197a9b449408ffb063e7fa967013cccb27b5be5e
parent 5976d8f266f1559b2c3abe2536bf51629217f6c8
author Suthikulpanit, Suravee <Suravee.Suthikulpanit@amd.com> 1553069548 +0000
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1556350483 +0200

Revert "svm: Fix AVIC incomplete IPI emulation"

commit 4a58038b9e420276157785afa0a0bbb4b9bc2265 upstream.

This reverts commit bb218fbcfaaa3b115d4cd7a43c0ca164f3a96e57.

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 bb218fbcfaaa 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>