linux-kernel - Re: [RFC PATCH v2 05/18] KVM: TDX: Drop superfluous page pinning in S-EPT management

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Message-ID: <aLIjelexDYa5dtkn@google.com>
Date: Fri, 29 Aug 2025 15:02:34 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Rick P Edgecombe <rick.p.edgecombe@...el.com>
Cc: Kai Huang <kai.huang@...el.com>, "ackerleytng@...gle.com" <ackerleytng@...gle.com>, 
	Vishal Annapurve <vannapurve@...gle.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Yan Y Zhao <yan.y.zhao@...el.com>, 
	Ira Weiny <ira.weiny@...el.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>, 
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "michael.roth@....com" <michael.roth@....com>
Subject: Re: [RFC PATCH v2 05/18] KVM: TDX: Drop superfluous page pinning in
 S-EPT management

On Fri, Aug 29, 2025, Rick P Edgecombe wrote:
> On Fri, 2025-08-29 at 13:19 -0700, Sean Christopherson wrote:
> > I'm happy to include more context in the changelog, but I really don't want
> > anyone to walk away from this thinking that pinning pages in random KVM code
> > is at all encouraged.
> 
> Sorry for going on a tangent. Defensive programming inside the kernel is a
> little more settled. But for defensive programming against the TDX module, there
> are various schools of thought internally. Currently we rely on some
> undocumented behavior of the TDX module (as in not in the spec) for correctness.

Examples?

> But I don't think we do for security.
> 
> Speaking for Yan here, I think she was a little more worried about this scenario
> then me, so I read this verbiage and thought to try to close it out.