linux-kernel - Re: [PATCH v6 2/2] kvm: sev: If ccp is busy, report busy to guest

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Message-ID: <CAAH4kHaeMgzdNP6Y7zdkdODransNkP4UiQ8ROpCVgenpiveJ_Q@mail.gmail.com>
Date: Thu, 5 Jun 2025 13:45:42 -0700
From: Dionna Amalie Glaze <dionnaglaze@...gle.com>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-coco@...ts.linux.dev, Paolo Bonzini <pbonzini@...hat.com>, 
	Joerg Roedel <jroedel@...e.de>, Peter Gonda <pgonda@...gle.com>, Borislav Petkov <bp@...en8.de>, 
	Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH v6 2/2] kvm: sev: If ccp is busy, report busy to guest

On Thu, Jun 5, 2025 at 12:15 PM Tom Lendacky <thomas.lendacky@....com> wrote:
>
> On 6/5/25 10:02, Dionna Glaze wrote:
> > The ccp driver can be overloaded even with guest request rate limits.
> > The return value of -EBUSY means that there is no firmware error to
> > report back to user space, so the guest VM would see this as
> > exitinfo2 = 0. The false success can trick the guest to update its
> > message sequence number when it shouldn't have.
>
> -EBUSY from the CCP driver is an error, not a throttling condition. Either

Ah, okay thanks Tom. I'll drop it for v6. I'll see how the first patch
is received before cutting a new email.

-- 
-Dionna Glaze, PhD, CISSP, CCSP (she/her)