linux-kernel - Re: [PATCH v4 2/2] 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.

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Message-ID: <CAAH4kHYiDpE9m4fhnUPkWrBq=pmDwVGx_--zSSjw1wE8irXESQ@mail.gmail.com>
Date: Wed, 14 May 2025 11:47:03 -0700
From: Dionna Amalie Glaze <dionnaglaze@...gle.com>
To: kvm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev, 
	Thomas Lendacky <Thomas.Lendacky@....com>, 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 v4 2/2] 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.

On Wed, May 14, 2025 at 11:42 AM Dionna Glaze <dionnaglaze@...gle.com> wrote:
>
> Instead, when ccp returns -EBUSY, that is reported to userspace as the
> throttling return value.
>

Ah, disregard this email. Globbed one too many patch files.


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