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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
Date: Thu, 15 Aug 2019 23:05:47 +0200
Message-ID: <20190815210547.GL15313@zn.tnic> (raw)
In-Reply-To: <a24a2c7d-cfab-a049-37e8-7260a9063a7c@citrix.com>

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.

Good mailing practices for 400: avoid top-posting and trim the reply.

  parent reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14 21:17 Lendacky, Thomas
2019-08-14 23:24 ` Non-random RDRAND " Pavel Machek
2019-08-14 23:38   ` Pavel Machek
2019-08-15 13:01   ` Lendacky, Thomas
2019-08-15 15:12   ` Theodore Y. Ts'o
2019-08-16  9:07     ` Pavel Machek
2019-08-16 14:42     ` Neil Horman
2019-08-15  7:21 ` Borislav Petkov
2019-08-15 13:47   ` Lendacky, Thomas
2019-08-15 15:34     ` Borislav Petkov
2019-08-15 20:14       ` Thomas Gleixner
2019-08-15 20:59 ` Andrew Cooper
2019-08-15 21:04   ` Thomas Gleixner
2019-08-15 21:05   ` Borislav Petkov [this message]
2019-08-15 21:25     ` Andrew Cooper
2019-08-17  8:44       ` Borislav Petkov
2019-08-17 11:43         ` Andrew Cooper
2019-08-18 16:32           ` Thomas Gleixner
2019-08-16 15:19 ` Andy Lutomirski

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