linux-kernel - Re: [PATCH] KVM: x86/mmu: preserve pending TLB flush across calls to kvm_tdp_mmu_zap

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Message-ID: <YGynf54vwWpyxhz4@kroah.com>
Date:   Tue, 6 Apr 2021 20:25:03 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        seanjc@...gle.com, stable@...r.kernel.org
Subject: Re: [PATCH] KVM: x86/mmu: preserve pending TLB flush across calls to
 kvm_tdp_mmu_zap_sp

On Tue, Apr 06, 2021 at 12:25:50PM -0400, Paolo Bonzini wrote:
> Right now, if a call to kvm_tdp_mmu_zap_sp returns false, the caller
> will skip the TLB flush, which is wrong.  There are two ways to fix
> it:
> 
> - since kvm_tdp_mmu_zap_sp will not yield and therefore will not flush
>   the TLB itself, we could change the call to kvm_tdp_mmu_zap_sp to
>   use "flush |= ..."
> 
> - or we can chain the flush argument through kvm_tdp_mmu_zap_sp down
>   to __kvm_tdp_mmu_zap_gfn_range.
> 
> This patch does the former to simplify application to stable kernels.
> 
> Cc: seanjc@...gle.com
> Fixes: 048f49809c526 ("KVM: x86/mmu: Ensure TLBs are flushed for TDP MMU during NX zapping")
> Cc: <stable@...r.kernel.org> # 5.10.x: 048f49809c: KVM: x86/mmu: Ensure TLBs are flushed for TDP MMU during NX zapping
> Cc: <stable@...r.kernel.org> # 5.10.x: 33a3164161: KVM: x86/mmu: Don't allow TDP MMU to yield when recovering NX pages
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Is this for only the stable kernels, or is it addressed toward upstream
merges?

Confused,

greg k-h