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From: Dave Hansen <dave.hansen@intel.com>
To: Adam Dunlap <acdunlap@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Arjan van de Ven <arjan@linux.intel.com>,
	Wei Liu <wei.liu@kernel.org>,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
	Jacob Xu <jacobhxu@google.com>, Alper Gun <alpergun@google.com>,
	Kevin Loughlin <kevinloughlin@google.com>,
	Peter Gonda <pgonda@google.com>, Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH v3] x86/asm: Force native_apic_mem_read to use mov
Date: Thu, 8 Feb 2024 08:47:46 -0800	[thread overview]
Message-ID: <168b4e3b-8076-4fc3-92bc-fcd9f2b516a8@intel.com> (raw)
In-Reply-To: <20240206223620.1833276-1-acdunlap@google.com>

On 2/6/24 14:36, Adam Dunlap wrote:
...
> In particular, when compiled with clang and run as a SEV-ES or
> SEV-SNP guest, the compiler would emit a testl instruction which is 
> not supported by the SEV-ES emulator

What changed?  Why is this a bug that we're only noticing now?  The line
of code that's modified here is from 2008.

I assume that it's something new in clang, but it'd be great to know
that for sure.

Also, considering the age of the last commit to touch that line:

Fixes: 67c5fc5c330f ("x86: merge apic_32/64.h")

this seems like the kind of thing we'll want in -stable in case folks
are compiling stable kernels with new clangs.

  reply	other threads:[~2024-02-08 16:48 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-06 22:36 Adam Dunlap
2024-02-08 16:47 ` Dave Hansen [this message]
2024-02-09 15:22   ` Ard Biesheuvel
2024-02-09 18:20     ` Adam Dunlap
2024-03-14 15:57       ` Kevin Loughlin
2024-03-15 23:44 ` Thomas Gleixner
2024-03-18 23:09   ` [PATCH v4] x86/asm: Force native_apic_mem_read() to use the MOV instruction Adam Dunlap
2024-03-19 11:27     ` Ard Biesheuvel
2024-04-08 13:43     ` [tip: x86/urgent] x86/apic: " tip-bot2 for Adam Dunlap

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