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From: "Gerd Hoffmann" <kraxel@redhat.com>
To: Tom Lendacky <thomas.lendacky@amd.com>
Cc: devel@edk2.groups.io, Ard Biesheuvel <ardb+tianocore@kernel.org>,
	 Jiewen Yao <jiewen.yao@intel.com>,
	Jordan Justen <jordan.l.justen@intel.com>,
	 Erdem Aktas <erdemaktas@google.com>,
	James Bottomley <jejb@linux.ibm.com>,
	 Min Xu <min.m.xu@intel.com>, Michael Roth <michael.roth@amd.com>
Subject: Re: [edk2-devel] [PATCH] OvmfPkg/ResetVector: Fix assembler bit test flag check
Date: Tue, 19 Sep 2023 09:59:28 +0200	[thread overview]
Message-ID: <hu4g52ctgcbyvuol6y27tvcxr5xzs34pmysd5xapzcdaudurkz@srd6ornzqg2a> (raw)
In-Reply-To: <f1e2264e03edf91c1020b989e123c332d3754376.1689366506.git.thomas.lendacky@amd.com>

On Fri, Jul 14, 2023 at 03:28:26PM -0500, Tom Lendacky wrote:
> Commit 63c50d3ff2854a76432b752af4f2a76f33ff1974 changed the check that is
> used to determine if SEV-ES is active. Originally, a CMP instruction with
> a supporting JZ instruction was used for the check. It was changed to use
> the BT instruction but not JZ instruction. The result of a BT instruction
> changes the the carry flag (CF) and not the zero flag (ZF). As a result,
> the wrong condition is being checked. Update the JZ to a JNC to properly
> detect if SEV-ES is active.

What is the effect of this bug?  Is it just the encryption sanity check
being skipped?

take care,
  Gerd



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  parent reply	other threads:[~2023-09-19  7:59 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-14 20:28 [PATCH] OvmfPkg/ResetVector: Fix assembler bit test flag check Lendacky, Thomas
2023-07-15  0:26 ` Ard Biesheuvel
2023-09-19  7:59 ` Gerd Hoffmann [this message]
2023-09-19 13:19   ` [edk2-devel] " Lendacky, Thomas via groups.io

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