linux-kernel - Re: [PATCH v2 1/1] x86/rdrand: disable RDSEED on AMD Cyan Skillfish

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Message-ID: <cfb12298-5214-4fc1-859c-2218c7da4ce3@intel.com>
Date: Tue, 17 Jun 2025 13:21:23 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Borislav Petkov <bp@...en8.de>, Mikhail Paulyshka <me@...aill.net>
Cc: Mario Limonciello <mario.limonciello@....com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] x86/rdrand: disable RDSEED on AMD Cyan Skillfish

On 6/17/25 13:05, Borislav Petkov wrote:
> +	/* Disable RDSEED on AMD Cyan Skillfish because of an error. */
> +	if (c->x86_model == 0x47 && c->x86_stepping == 0x0) {
> +		clear_cpu_cap(c, X86_FEATURE_RDSEED);
> +		msr_clear_bit(MSR_AMD64_CPUID_FN_7, 18);
> +		pr_emerg("RDSEED is not reliable on this platform; disabling.\n");
> +	}

Heh, maybe if x86_init_rdrand() did RDSEED too, this wouldn't have
slipped through QA.