linux-kernel - Re: [PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops

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Date:	Thu, 17 Sep 2015 04:22:50 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>
CC:	Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
	Paolo Bonzini <pbonzini@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	KVM list <kvm@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	xen-devel <Xen-devel@...ts.xen.org>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops

However, the difference between one CONFIG and another is quite frankly crazy.  We should explicitly use the safe versions where this is appropriate, and then yes, we should do this.

Yet another reason the paravirt code is batshit crazy.

On September 17, 2015 2:31:34 AM PDT, Borislav Petkov <bp@...en8.de> wrote:
>On Thu, Sep 17, 2015 at 09:19:20AM +0200, Ingo Molnar wrote:
>> Most big distro kernels on bare metal have CONFIG_PARAVIRT=y (I
>checked Ubuntu and 
>> Fedora), so we are potentially exposing a lot of users to problems.
>
>+ SUSE.
>
>> Crashing the bootup on an unknown MSR is bad. Many MSR reads and
>writes are 
>> non-critical and returning the 'safe' result is much better than
>crashing or 
>> hanging the bootup.
>
>... and prepending all MSR accesses with feature/CPUID checks is
>probably almost
>impossible.

-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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