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SubjectRe: [tip: x86/urgent] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h
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On 8/24/19 11:19 AM, Pavel Machek wrote:
> On Fri 2019-08-23 01:10:49, tip-bot2 for Tom Lendacky wrote:
>> The following commit has been merged into the x86/urgent branch of tip:
>>
>> Commit-ID: c49a0a80137c7ca7d6ced4c812c9e07a949f6f24
>> Gitweb: https://git.kernel.org/tip/c49a0a80137c7ca7d6ced4c812c9e07a949f6f24
>> Author: Tom Lendacky <thomas.lendacky@amd.com>
>> AuthorDate: Mon, 19 Aug 2019 15:52:35
>> Committer: Borislav Petkov <bp@suse.de>
>> CommitterDate: Mon, 19 Aug 2019 19:42:52 +02:00
>>
>> x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h
>>
>> There have been reports of RDRAND issues after resuming from suspend on
>> some AMD family 15h and family 16h systems. This issue stems from a BIOS
>> not performing the proper steps during resume to ensure RDRAND continues
>> to function properly.
>
> There are quite a few unanswered questions here.
>
> a) Is there/should there be CVE for this?
>
> b) Can we perform proper steps in kernel, thus making RDRAND usable
> even when BIOS is buggy?
>

The kernel should at least be able to set its internal "CPUID" bit, visible
through /proc/cpuinfo.

-hpa

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