Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 25 Apr 2023 23:06:54 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Tony Battersby <tonyb@cybernetics.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Mario Limonciello <mario.limonciello@amd.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC] x86/cpu: fix intermittent lockup on poweroff
Message-ID: <20230425210654.GFZEhA7p7p/FXht76v@fat_crate.local>
References: <3817d810-e0f1-8ef8-0bbd-663b919ca49b@cybernetics.com>
 <f5c7a104-d422-bd02-d361-e9e9f433d41d@intel.com>
 <1955637d-b7ab-20a8-558a-6b909b7069a9@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <1955637d-b7ab-20a8-558a-6b909b7069a9@intel.com>
Precedence: bulk

On Tue, Apr 25, 2023 at 01:34:48PM -0700, Dave Hansen wrote:
> >    0x0000000b 0x00: eax=0x00000001 ebx=0x00000002 ecx=0x00000100 edx=0x00000000
> 
> which does have BIT(0) set.

Yeah, or the last basic leaf

  0x0000000b 0x01: eax=0x00000005 ebx=0x0000000c ecx=0x00000201 edx=0x00000000

but that one has bit 0 set too, so yeah, patch is correct. I'll queue it
after -rc1.

But Tony, please change your commit message to say something like this:

"Check the maximum supported extended CPUID level because on Intel,
querying an invalid extended CPUID leaf returns the values of the
maximum basic CPUID leaf and if bit  0 in EAX is set, the check falsely
evaluates to true and WBINVD is wrongly executed where it shouldn't."

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette