linux-kernel - Re: [PATCH 05/21] KVM: VMX: Teach EPT violation helper about private mem

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Message-ID: <3936872ab5bd396051a67f46b92a44e4b35fba45.camel@intel.com>
Date: Wed, 11 Sep 2024 16:29:57 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Gao, Chao" <chao.gao@...el.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "Huang, Kai" <kai.huang@...el.com>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>, "Zhao, Yan Y"
	<yan.y.zhao@...el.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "nik.borisov@...e.com"
	<nik.borisov@...e.com>, "dmatlack@...gle.com" <dmatlack@...gle.com>
Subject: Re: [PATCH 05/21] KVM: VMX: Teach EPT violation helper about private
 mem

On Wed, 2024-09-11 at 16:52 +0800, Chao Gao wrote:
> > +       /*
> > +        * Don't rely on GFN's attribute tracking xarray to prevent EPT
> > violation
> > +        * loops.
> > +        */
> 
> The comment seems a bit odd to me. We cannot use the gfn attribute from the
> attribute xarray simply because here we need to determine if *this access* is
> to private memory, which may not match the gfn attribute. Even if there are
> other ways to prevent an infinite EPT violation loop, we still need to check
> the shared bit in the faulting GPA.

Yea this comment is not super informative. We can probably just drop it.