linux-kernel - Re: [PATCH v3 0/8] x86, KVM: Optimize SEV cache flushing

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Message-ID: <aG6X__K8MvVYORkr@google.com>
Date: Wed, 9 Jul 2025 09:25:35 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Paolo Bonzini <pbonzini@...hat.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, linux-kernel@...r.kernel.org, 
	kvm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	Kevin Loughlin <kevinloughlin@...gle.com>, Tom Lendacky <thomas.lendacky@....com>, 
	Kai Huang <kai.huang@...el.com>, Ingo Molnar <mingo@...nel.org>, 
	Zheyun Shen <szy0127@...u.edu.cn>, Mingwei Zhang <mizhang@...gle.com>, 
	Francesco Lavra <francescolavra.fl@...il.com>
Subject: Re: [PATCH v3 0/8] x86, KVM: Optimize SEV cache flushing

On Thu, May 22, 2025, Sean Christopherson wrote:
> This is the combination of Kevin's WBNOINVD series[1] with Zheyun's targeted
> flushing series[2].  The combined goal is to use WBNOINVD instead of WBINVD
> when doing cached maintenance to prevent data corruption due to C-bit aliasing,
> and to reduce the number of cache invalidations by only performing flushes on
> CPUs that have entered the relevant VM since the last cache flush.
> 
> All of the non-KVM patches are frontloaded and based on v6.15-rc7, so that
> they can go through the tip tree (in a stable branch, please :-) ).

Tip tree folks, any feedback/thoughts on this series (patches 1-4 in particular)?
It'd be nice to get this into 6.17, and I'd really like land it by 6.18 at the
latest.

> Kevin Loughlin (2):
>   x86, lib: Add WBNOINVD helper functions
>   KVM: SEV: Prefer WBNOINVD over WBINVD for cache maintenance efficiency
> 
> Sean Christopherson (3):
>   drm/gpu: Remove dead checks on wbinvd_on_all_cpus()'s return value
>   x86, lib: Drop the unused return value from wbinvd_on_all_cpus()
>   KVM: x86: Use wbinvd_on_cpu() instead of an open-coded equivalent
> 
> Zheyun Shen (3):
>   x86, lib: Add wbinvd and wbnoinvd helpers to target multiple CPUs
>   KVM: SVM: Remove wbinvd in sev_vm_destroy()
>   KVM: SVM: Flush cache only on CPUs running SEV guest
> 
>  arch/x86/include/asm/smp.h           | 23 +++++++-
>  arch/x86/include/asm/special_insns.h | 32 ++++++++++-
>  arch/x86/kvm/svm/sev.c               | 85 +++++++++++++++++++---------
>  arch/x86/kvm/svm/svm.h               |  1 +
>  arch/x86/kvm/x86.c                   | 11 +---
>  arch/x86/lib/cache-smp.c             | 26 ++++++++-
>  drivers/gpu/drm/drm_cache.c          |  9 +--
>  7 files changed, 140 insertions(+), 47 deletions(-)
> 
> 
> base-commit: a5806cd506af5a7c19bcd596e4708b5c464bfd21
> -- 
> 2.49.0.1151.ga128411c76-goog
>