linux-kernel - Re: [PATCH 2/2] x86/rdrand: hide RDRAND and RDSEED from CPUID in case of a malfunction

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Message-ID: <2916bccf-a252-4a57-bb4b-efb8703fd909@mixaill.net>
Date: Wed, 12 Mar 2025 16:36:13 +0300
From: Mikhail Paulyshka <me@...aill.net>
To: Borislav Petkov <bp@...en8.de>
Cc: 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 2/2] x86/rdrand: hide RDRAND and RDSEED from CPUID in case
 of a malfunction

On 3/12/25 3:45 PM, Borislav Petkov wrote:
> On Wed, Mar 12, 2025 at 03:31:30PM +0300, Mikhail Paulyshka wrote:
>> @@ -46,6 +47,8 @@ void x86_init_rdrand(struct cpuinfo_x86 *c)
>>   
>>   	if (failure) {
>>   		clear_cpu_cap(c, X86_FEATURE_RDRAND);
>> +		if (c->x86_vendor == X86_VENDOR_AMD || c->x86_vendor == X86_VENDOR_HYGON)
> Hygon is family 0x18. Have you tested it there?

My bad, I thought Hygon is backwards compatible with AMD Zen1/2. Then it 
can be removed in case Hygon's MSRs are different.