Subject: Re: [PATCH v3 08/12] KVM: Propagate vcpu explicitly to mark_page_dirty_in_slot()

From: Marc Zyngier <[email-masked]>
Date: Wed, 17 Nov 2021 18:13:37 +0000

On Wed, 17 Nov 2021 17:39:59 +0000,
David Woodhouse <[email-masked]> wrote:
> 
> From: David Woodhouse <[email-masked]>
> 
> The kvm_dirty_ring_get() function uses kvm_get_running_vcpu() to work out
> which dirty ring to use, but there are some use cases where that doesn't
> work.
> 
> There's one in setting the Xen shared info page, introduced in commit
> 629b5348841a ("KVM: x86/xen: update wallclock region") and reported by
> "butt3rflyh4ck" <[email-masked]> in
> https://lore.kernel.org/kvm/[email-masked]/
> 
> There's also about to be another one when the newly-reintroduced
> gfn_to_pfn_cache needs to mark a page as dirty from the MMU notifier
> which invalidates the mapping. In that case, we will *know* the vcpu
> that can be 'blamed' for dirtying the page, and we just need to be
> able to pass it in as an explicit argument when doing so.
> 
> This patch preemptively resolves the second issue, and paves the way
> for resolving the first. A complete fix for the first issue will need
> us to switch the Xen shinfo to be owned by a particular vCPU, which
> will happen in a separate patch.
> 
> Signed-off-by: David Woodhouse <[email-masked]>
> ---
>  arch/arm64/kvm/mmu.c           |  2 +-
>  arch/x86/kvm/mmu/mmu.c         |  2 +-
>  arch/x86/kvm/mmu/spte.c        |  2 +-
>  arch/x86/kvm/mmu/tdp_mmu.c     |  2 +-
>  arch/x86/kvm/x86.c             |  4 ++--
>  include/linux/kvm_dirty_ring.h |  6 ++++--
>  include/linux/kvm_host.h       |  3 ++-
>  virt/kvm/dirty_ring.c          |  8 ++++++--
>  virt/kvm/kvm_main.c            | 18 +++++++++---------
>  9 files changed, 27 insertions(+), 20 deletions(-)

What's the base for this series? This patch fails to compile for me
(at least on arm64), and the following patch doesn't apply on -rc1.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.