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: Fri, 24 May 2024 09:50:26 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>
CC: Sean Christopherson <seanjc@...gle.com>, Kai Huang <kai.huang@...el.com>,
	Rick P Edgecombe <rick.p.edgecombe@...el.com>, "dmatlack@...gle.com"
	<dmatlack@...gle.com>, "sagis@...gle.com" <sagis@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Erdem Aktas
	<erdemaktas@...gle.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>
Subject: Re: [PATCH 02/16] KVM: x86/mmu: Introduce a slot flag to zap only
 slot leafs on slot deletion

On Wed, May 22, 2024 at 05:45:39PM +0200, Paolo Bonzini wrote:
> On Wed, May 22, 2024 at 8:49 AM Yan Zhao <yan.y.zhao@...el.com> wrote:
> > > Disabling the quirk would allow KVM to choose between a slow/precise/partial zap,
> > > and full/fast zap.
> > TDX needs to disable the quirk for slow/precise/partial zap, right?
> 
> Yes - and since TDX is a separate VM type it might even start with the
> quirk disabled. For sure, the memslot flag is the worst option and I'd
> really prefer to avoid it.
Thanks. Will implement a quirk and let TDX code in QEMU to disable the
quirk.

> 
> > > I have the same feeling that the bug is probably not reproducible with latest
> > > KVM code
> 
> Or with the latest QEMU code, if it was related somehow to non-atomic
> changes to the memory map.
>
Thanks for this input. Will check if it's related.