From: Paolo Bonzini <pbonzini@redhat.com>
To: Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
KVM list <kvm@vger.kernel.org>,
Arjan van de Ven <arjan@linux.intel.com>,
xen-devel <Xen-devel@lists.xen.org>,
linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrew Morton <akpm@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops
Date: Thu, 17 Sep 2015 13:39:26 +0200 [thread overview]
Message-ID: <55FAA66E.1070401@redhat.com> (raw)
In-Reply-To: <20150917093134.GC12316@nazgul.tnic>
On 17/09/2015 11:31, Borislav Petkov wrote:
>
>> > 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.
That's not a big deal, that's what *_safe is for. The problem is that
there are definitely some cases where the *_safe version is not being used.
I agree with Ingo that we should start with a WARN. For example:
- give the read_msr and write_msr hooks the same prototype as the safe
variants
- make the virt platforms always return "no error" for the unsafe
variants (I understand if your first reaction is "ouch", but this
effectively is already the current behavior)
- change rdmsr/wrmsr/rdmsrl/wrmsrl to WARN if the read_msr and write_msr
hooks return an error
Paolo
next prev parent reply other threads:[~2015-09-17 11:39 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-16 23:33 [PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops Andy Lutomirski
2015-09-16 23:33 ` [PATCH 1/3] x86/paravirt: Add _safe to the read_msr and write_msr PV hooks Andy Lutomirski
2015-09-16 23:33 ` [PATCH 2/3] x86/paravirt: Add paravirt_{read,write}_msr Andy Lutomirski
2015-09-16 23:33 ` [PATCH 3/3] x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y Andy Lutomirski
2015-09-17 7:19 ` [PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops Ingo Molnar
2015-09-17 9:31 ` Borislav Petkov
2015-09-17 11:22 ` H. Peter Anvin
2015-09-17 11:39 ` Paolo Bonzini [this message]
2015-09-17 15:27 ` Borislav Petkov
2015-09-17 15:32 ` [Xen-devel] " Andrew Cooper
2015-09-17 15:37 ` Borislav Petkov
2015-09-17 15:23 ` Andy Lutomirski
2015-09-17 15:27 ` Arjan van de Ven
2015-09-17 15:29 ` Paolo Bonzini
2015-09-17 15:31 ` Arjan van de Ven
2015-09-17 15:33 ` Paolo Bonzini
2015-09-17 17:30 ` Ingo Molnar
2015-09-17 18:51 ` Andy Lutomirski
2015-09-17 8:58 ` Peter Zijlstra
2015-09-17 11:40 ` Paolo Bonzini
2015-09-17 12:27 ` Peter Zijlstra
2015-09-17 15:17 ` Andy Lutomirski
2015-09-17 15:17 ` Peter Zijlstra
2015-09-17 15:26 ` Andy Lutomirski
2015-09-17 15:29 ` Paolo Bonzini
2015-09-17 9:10 ` [Xen-devel] " Andrew Cooper
2015-09-17 15:11 ` Boris Ostrovsky
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