Re: [PATCH] KVM: x86/mmu: preserve pending TLB flush across calls to kvm_tdp_mmu_zap_sp

[Paolo Bonzini]

On 06/04/21 20:25, Greg KH wrote:
> 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@xxxxxxxxxx
> > Fixes: 048f49809c526 ("KVM: x86/mmu: Ensure TLBs are flushed for TDP MMU during NX zapping")
> > Cc: <stable@xxxxxxxxxxxxxxx> # 5.10.x: 048f49809c: KVM: x86/mmu: Ensure TLBs are flushed for TDP MMU during NX zapping
> > Cc: <stable@xxxxxxxxxxxxxxx> # 5.10.x: 33a3164161: KVM: x86/mmu: Don't allow TDP MMU to yield when recovering NX pages
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > ---
> >   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,

It's for upstream.  I'll include it (with the expected "[ Upstream 
commit abcd ]" header) when I post the complete backport.  I'll send 
this patch to Linus as soon as I get a review even if I don't have 
anything else in the queue, so (as a general idea) the full backport 
should be sent and tested on Thursday-Friday.

Paolo