Re: [PATCH v11 050/113] KVM: x86/tdp_mmu: Ignore unsupported mmu operation on private GFNs

[Isaku Yamahata]

On Tue, Jan 17, 2023 at 02:40:46AM +0000,
"Huang, Kai" <kai.huang@xxxxxxxxx> wrote:

> On Thu, 2023-01-12 at 08:31 -0800, isaku.yamahata@xxxxxxxxx wrote:
> > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> > 
> > Some KVM MMU operations (dirty page logging, page migration, aging page)
> > aren't supported for private GFNs (yet) with the first generation of TDX.
> > Silently return on unsupported TDX KVM MMU operations.
> > 
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> 
> 
> You already have previous patches to do similar things:
> 
> [PATCH v11 034/113] KVM: x86/mmu: Disallow fast page fault on private GPA
> [PATCH v11 043/113] KVM: x86/tdp_mmu: Don't zap private pages for unsupported
> cases
> [PATCH v11 048/113] KVM: x86/mmu: Disallow dirty logging for x86 TDX
> [PATCH v11 049/113] KVM: x86/mmu: TDX: Do not enable page track for TD guest
> 
> Now you have this patch:
> 
> [PATCH v11 050/113] KVM: x86/tdp_mmu: Ignore unsupported mmu operation on
> private GFNs
> 
> They are very confusing to me.  Those previous patches are all "unsupported
> operations", correct? 
> 
> For instance, this patch says "dirty page logging isn't supported for private
> GFNs" (and why there's a 'yet' after it?), so based on the patch title my
> understanding is you are going to _ignore_ "dirty page logging".  But you
> already have a previous patch to "Disallow dirty logging for x86 TDX".  
> 
> Shouldn't the two be in the same patch?  Or you were trying to highlight the
> different between "x86/mmu" and "x86/tdp_mmu"?
> 
> Please try to make the whole thing more clear.  My first glance is, if it was
> me, I would probably have _ONE_ dedicated patch for _EACH_ unsupported
> operation, and make it very clear in the patch title.  But you may have your own
> way to make things more clearer.

Agreed, merged this patch into [PATCH v11 048/113] KVM: x86/mmu: Disallow dirty
logging for x86 TDX.
-- 
Isaku Yamahata <isaku.yamahata@xxxxxxxxx>