linux-kernel - Re: [PATCH] KVM: SEV: Fix guest memory leak when handling guest requests

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Message-ID: <ZkyrAETobNEjI4Tr@google.com>
Date: Tue, 21 May 2024 07:09:04 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Michael Roth <michael.roth@....com>
Cc: Michael Roth <mdroth@...xas.edu>, pbonzini@...hat.com, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, ashish.kalra@....com, thomas.lendacky@....com, 
	rick.p.edgecombe@...el.com
Subject: Re: [PATCH] KVM: SEV: Fix guest memory leak when handling guest requests

On Mon, May 20, 2024, Michael Roth wrote:
> On Mon, May 20, 2024 at 04:32:04PM -0700, Sean Christopherson wrote:
> > On Mon, May 20, 2024, Michael Roth wrote:
> > > But there is a possibility that the guest will attempt access the response
> > > PFN before/during that reporting and spin on an #NPF instead though. So
> > > maybe the safer more repeatable approach is to handle the error directly
> > > from KVM and propagate it to userspace.
> > 
> > I was thinking more along the lines of KVM marking the VM as dead/bugged.  
> 
> In practice userspace will get an unhandled exit and kill the vcpu/guest,
> but we could additionally flag the guest as dead.

Honest question, does it make sense from KVM to make the VM unusable?  E.g. is
it feasible for userspace to keep running the VM?  Does the page that's in a bad
state present any danger to the host?

> Is there a existing mechanism for this?

kvm_vm_dead()