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Message-ID: <f5c7a104-d422-bd02-d361-e9e9f433d41d@intel.com>
Date:   Tue, 25 Apr 2023 13:03:22 -0700
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Subject: Re: [PATCH RFC] x86/cpu: fix intermittent lockup on poweroff
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To:     Tony Battersby <tonyb@cybernetics.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
Cc:     "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>
References: <3817d810-e0f1-8ef8-0bbd-663b919ca49b@cybernetics.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <3817d810-e0f1-8ef8-0bbd-663b919ca49b@cybernetics.com>
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On 4/25/23 12:26, Tony Battersby wrote:
> -	if (cpuid_eax(0x8000001f) & BIT(0))
> +	if (c->extended_cpuid_level >= 0x8000001f &&
> +	    (cpuid_eax(0x8000001f) & BIT(0)))
>  		native_wbinvd();

Oh, so the existing code is running into the

> If a value entered for CPUID.EAX is higher than the maximum input
> value for basic or extended function for that processor then the data
> for the highest basic information leaf is returned
behavior.  It's basically looking at BIT(0) of some random extended
leaf.  Probably 0x80000008 based on your 'cpuid -r' output.