From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "linux-coco@lists.linux.dev" <linux-coco@lists.linux.dev>,
"Hansen, Dave" <dave.hansen@intel.com>,
"clopez@suse.de" <clopez@suse.de>,
"kas@kernel.org" <kas@kernel.org>,
"x86@kernel.org" <x86@kernel.org>
Cc: "ak@linux.intel.com" <ak@linux.intel.com>,
"bp@alien8.de" <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"hpa@zytor.com" <hpa@zytor.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Luck, Tony" <tony.luck@intel.com>,
"tglx@kernel.org" <tglx@kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH] x86/tdx: Fix zero-extension for CPUID emulation
Date: Tue, 12 May 2026 22:43:49 +0000 [thread overview]
Message-ID: <6e4422c1c6d5d0e6415b02e6cd2633c6e34030ff.camel@intel.com> (raw)
In-Reply-To: <d76284f1-79e2-4e7b-94e7-252ff3ee9e5e@intel.com>
On Tue, 2026-05-12 at 15:37 -0700, Dave Hansen wrote:
> On 5/12/26 15:24, Edgecombe, Rick P wrote:
> > On the other hand, the #VE handler is supposed to do the emulation of the
> > instruction, with the help of the TDVMCALL, so maybe the correctness should be
> > in the guest... Hmm...
>
> Maybe we should just change the GHCI spec.
>
> What if we said:
>
> | Operand | ... |
> | R12 (lower 32 bits) | EAX |
> | R13 (lower 32 bits) | EBX |
> | R14 (lower 32 bits) | ECX |
> | R15 (lower 32 bits) | EDX |
>
> Then said the upper 32 bits are undefined. Then the kernel *must* mask
> them to be correct. Then we don't have to do any checking at all and
> there's no ambiguity about what the VMM is allowed to do or what chaos
> it might cause.
Hmm, let me check. It intersects with the other guests/hosts, but hard to see
how the other ones could be out of spec and not be buggy.
next prev parent reply other threads:[~2026-05-12 22:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 21:37 [PATCH] x86/tdx: Fix zero-extension for CPUID emulation Carlos López
2026-05-12 21:48 ` Edgecombe, Rick P
2026-05-12 22:14 ` Dave Hansen
2026-05-12 22:24 ` Edgecombe, Rick P
2026-05-12 22:37 ` Dave Hansen
2026-05-12 22:43 ` Edgecombe, Rick P [this message]
2026-05-12 22:33 ` Carlos López
2026-05-12 22:15 ` Carlos López
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