linux-kernel - Re: [GIT pull] x86/urgent for 5.3-rc5

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Date:   Sun, 25 Aug 2019 10:18:02 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Borislav Petkov <bp@...e.de>
Cc:     Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [GIT pull] x86/urgent for 5.3-rc5

On Sun, Aug 25, 2019 at 2:45 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
>   - Clear the RDRAND CPUID bit on AMD family 15h and 16h CPUs which are
>     affected by broken firmware which does not initialize RDRAND correctly
>     after resume. Add a command line parameter to override this for machine
>     which either do not use suspend/resume or have a fixed
>     BIOS. Unfortunately there is no way to detect this on boot, so the only
>     safe decision is to turn it off by default.

Not doing the Zen 2 boot-time case? Everybody assumes that all
firmware has been fixed?

That one should be easy to verify since it happens at boot: just do
"rdrand" twice, and if it returns all-ones both times, it's broken.

              Linus