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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Message-ID: <CABgObfaq4oHC9C_iA2OudmFN-7E9RDiw-WiDu9skmpsW39j0nQ@mail.gmail.com>
Date: Wed, 22 May 2024 17:45:39 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Yan Zhao <yan.y.zhao@...el.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 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.

> > 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.

Paolo