Date:   Mon, 27 Feb 2023 14:00:05 -0800
From:   Isaku Yamahata <isaku.yamahata@gmail.com>
To:     "Huang, Kai" <kai.huang@intel.com>
Cc:     "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@intel.com>,
        "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "Shahar, Sagi" <sagis@google.com>,
        "Aktas, Erdem" <erdemaktas@google.com>,
        "isaku.yamahata@gmail.com" <isaku.yamahata@gmail.com>,
        "dmatlack@google.com" <dmatlack@google.com>,
        "Christopherson,, Sean" <seanjc@google.com>
Subject: Re: [PATCH v11 050/113] KVM: x86/tdp_mmu: Ignore unsupported mmu
 operation on private GFNs
Message-ID: <20230227220005.GO4175971@ls.amr.corp.intel.com>
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On Tue, Jan 17, 2023 at 02:40:46AM +0000,
"Huang, Kai" <kai.huang@intel.com> wrote:

> On Thu, 2023-01-12 at 08:31 -0800, isaku.yamahata@intel.com wrote:
> > From: Isaku Yamahata <isaku.yamahata@intel.com>
> > 
> > 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@intel.com>
> 
> 
> 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@gmail.com>