linux-kernel - Re: [PATCH] KVM: x86/mmu: Stop zapping invalidated TDP MMU roots asynchronously

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Message-ID: <2023102145-unstylish-vertigo-ab7c@gregkh>
Date:   Sat, 21 Oct 2023 11:10:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     David Matlack <dmatlack@...gle.com>
Cc:     Sean Christopherson <seanjc@...gle.com>, stable@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pattara Teerapong <pteerapong@...gle.com>,
        David Stevens <stevensd@...gle.com>,
        Yiwei Zhang <zzyiwei@...gle.com>,
        Paul Hsia <paulhsia@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH] KVM: x86/mmu: Stop zapping invalidated TDP MMU roots
 asynchronously

On Fri, Oct 20, 2023 at 11:52:34AM -0700, David Matlack wrote:
> On 2023-10-19 01:11 PM, Sean Christopherson wrote:
> > [ Upstream commit 0df9dab891ff0d9b646d82e4fe038229e4c02451 ]
> > 
> > Stop zapping invalidate TDP MMU roots via work queue now that KVM
> > preserves TDP MMU roots until they are explicitly invalidated.  Zapping
> > roots asynchronously was effectively a workaround to avoid stalling a vCPU
> > for an extended during if a vCPU unloaded a root, which at the time
> > happened whenever the guest toggled CR0.WP (a frequent operation for some
> > guest kernels).
> > 
> [...]
> > 
> > Reported-by: Pattara Teerapong <pteerapong@...gle.com>
> > Cc: David Stevens <stevensd@...gle.com>
> > Cc: Yiwei Zhang<zzyiwei@...gle.com>
> > Cc: Paul Hsia <paulhsia@...gle.com>
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > Message-Id: <20230916003916.2545000-4-seanjc@...gle.com>
> > Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> > Cc: David Matlack <dmatlack@...gle.com>
> > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > ---
> 
> Reviewed-by: David Matlack <dmatlack@...gle.com>
> Tested-by: David Matlack <dmatlack@...gle.com>
> 
> (Ran all KVM selftests and kvm-unit-tests with lockdep enabled.)

Thanks, now queued up.

greg k-h