linux-kernel - Re: [PATCH 1/2] KVM: x86: fix APIC page invalidation

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Date:   Wed, 13 Dec 2017 12:54:34 +0000
From:   Richard Purdie <richard.purdie@...uxfoundation.org>
To:     Radim Krčmář <rkrcmar@...hat.com>,
        Fabian Grünbichler 
        <f.gruenbichler@...xmox.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        stable <stable@...nel.org>
Subject: Re: [PATCH 1/2] KVM: x86: fix APIC page invalidation

On Thu, 2017-11-30 at 19:05 +0100, Radim Krčmář wrote:
> Implementation of the unpinned APIC page didn't update the VMCS
> address
> cache when invalidation was done through range mmu notifiers.
> This became a problem when the page notifier was removed.
> 
> Re-introduce the arch-specific helper and call it from
> ...range_start.
> 
> Fixes: 38b9917350cb ("kvm: vmx: Implement set_apic_access_page_addr")
> Fixes: 369ea8242c0f ("mm/rmap: update to new mmu_notifier semantic
> v2")
> Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  3 +++
>  arch/x86/kvm/x86.c              | 14 ++++++++++++++
>  virt/kvm/kvm_main.c             |  8 ++++++++
>  3 files changed, 25 insertions(+)

Thanks for this. I've been chasing APIC related hangs booting images
with qemu-system-x86_64 on 4.13 and 4.14 host kernels where the guest
doesn't have x2apic enabled.

I can confirm this fixes issues the Yocto Project automated testing
infrastructure was seeing.

I'd like to add support for backporting this in stable.

Tested-by: Richard Purdie <richard.purdie@...uxfoundation.org>

Cheers,

Richard