Re: [stable-4.19] kvm: nVMX: NMI-window and interrupt-window exiting should wake L2 from HLT

[Sasha Levin <sashal@kernel.org>]

On Sat, Apr 06, 2019 at 07:43:45PM -0400, Mark Mielke wrote:
>This commit was first released with 5.0:
>
>commit 9ebdfe5230f2e50e3ba05c57723a06e90946815a
>Author: Jim Mattson <jmattson@google.com>
>Date:   Mon Nov 26 11:22:32 2018 -0800
>
>    kvm: nVMX: NMI-window and interrupt-window exiting should wake L2 from HLT
>
>    According to the SDM, "NMI-window exiting" VM-exits wake a logical
>    processor from the same inactive states as would an NMI and
>    "interrupt-window exiting" VM-exits wake a logical processor from the
>    same inactive states as would an external interrupt. Specifically, they
>    wake a logical processor from the shutdown state and from the states
>    entered using the HLT and MWAIT instructions.
>
>    Fixes: 6dfacadd5858 ("KVM: nVMX: Add support for activity state HLT")
>    Signed-off-by: Jim Mattson <jmattson@google.com>
>    Reviewed-by: Peter Shier <pshier@google.com>
>    Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
>    [Squashed comments of two Jim's patches and used the simplified code
>     hunk provided by Sean. - Radim]
>    Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
>
>This commit does not apply clean to 4.19, only due to restructuring
>that split out a portion of arch/x86/kvm/vmx.c into
>arch/x86/kvm/vmx/nested.c.
>
>The following procedure can be followed to allow the patch to apply
>clean to 4.19:
>
>git checkout linux-4.19.y
>git format-patch -1 9ebdfe5230f2e50e3ba05c57723a06e90946815a
>perl -pi -e 's[arch/x86/kvm/vmx/nested.c][arch/x86/kvm/vmx.c]g'
>0001-kvm-nVMX-NMI-window-and-interrupt-window-exiting-sho.patch
>git am 0001-kvm-nVMX-NMI-window-and-interrupt-window-exiting-sho.patch
>
>I have been using this patch in our own 4.19-based production
>environment (which heavily uses nested KVM for product simulation)
>since January, 2019, along with several other nVMX patches. All of the
>other nVMX patches have since made it into 4.19 except for this one. I
>expect this one did not make the stable list because it did not apply
>cleanly without help.
>
>I don't have a specific test to reproduce the problem that this fix
>addresses. I had specific problems that were addressed by other nVMX
>patches, but this was one I chose to add as a preventative measure
>based upon the description and the likelihood that the problem might
>impact us.
>
>Please consider including this patch into 4.19. I don't mind
>maintaining it local if there is some reason it doesn't qualify for
>stable. But, if this could help others, I'm happy to share the above
>method of getting it into 4.19 safely.

I've queued it for 4.19, thank you.

--
Thanks,
Sasha