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Date:   Thu, 15 Aug 2019 23:05:47 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Andrew Cooper <andrew.cooper3@citrix.com>
Cc:     "Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Pavel Machek <pavel@ucw.cz>, Chen Yu <yu.c.chen@intel.com>,
        Jonathan Corbet <corbet@lwn.net>
Subject: Re: [PATCH] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h
Message-ID: <20190815210547.GL15313@zn.tnic>
References: <776cb5c2d33e7fd0d2893904724c0e52b394f24a.1565817448.git.thomas.lendacky@amd.com>
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On Thu, Aug 15, 2019 at 09:59:03PM +0100, Andrew Cooper wrote:
> If you're virtualised, the write to MSR_AMD64_CPUID_FN_1 almost
> certainly won't take effect, which means userspace will still be able to
> see the bit.

msr_clear_bit() has a return value. We should check it before
doing anything further. I hope the HV actually signals the write
success/failure properly so that we get a correct return value.

-- 
Regards/Gruss,
    Boris.

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