linux-kernel - Re: [PATCH 02/16] KVM: x86/mmu: Introduce a slot flag to zap only slot leafs on slot deletion

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Date: Thu, 16 May 2024 02:21:40 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "seanjc@...gle.com" <seanjc@...gle.com>
CC: "Yang, Weijiang" <weijiang.yang@...el.com>, "isaku.yamahata@...il.com"
	<isaku.yamahata@...il.com>, "Huang, Kai" <kai.huang@...el.com>,
	"sagis@...gle.com" <sagis@...gle.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Aktas, Erdem" <erdemaktas@...gle.com>,
	"Zhao, Yan Y" <yan.y.zhao@...el.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"dmatlack@...gle.com" <dmatlack@...gle.com>
Subject: Re: [PATCH 02/16] KVM: x86/mmu: Introduce a slot flag to zap only
 slot leafs on slot deletion

On Wed, 2024-05-15 at 16:56 -0700, Rick Edgecombe wrote:
> 
> If we think it is not a security issue, and we don't even know if it can be
> hit
> for TDX, then I'd be included to go with (a). Especially since we are just
> aiming for the most basic support, and don't have to worry about regressions
> in
> the classical sense.
> 
> I'm not sure how easy it will be to root cause it at this point. Hopefully Yan
> will be coming online soon. She mentioned some previous Intel effort to
> investigate it. Presumably we would have to start with the old kernel that
> exhibited the issue. If it can still be found...
> 

Weijiang filled me in. It sounds like a really tough one, as he described: "From
my experience, to reproduce the issue, it requires specific HW config + specific
SW + specific operations, I almost died on it"

If it shows up in TDX, we might get lucky with an easier reproducer...