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From: Andy Lutomirski <luto@amacapital.net>
Date: Sat, 2 Apr 2016 08:13:36 -0700
Message-ID: <CALCETrWP33SR5TCA-baZi8xBrHpWe=wzkuvUM=y4x_MPt1XgYg@mail.gmail.com>
Subject: Re: [PATCH v5 0/9] Improve non-"safe" MSR access failure handling
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        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 Mailing List <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Borislav Petkov <bp@alien8.de>
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On Sat, Apr 2, 2016 at 7:24 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> This patch series looks much nicer than the last one. I assume you
> tested that the early-trap handling actually worked too? I only looked
> at the patches..
>
> Ack to it all,

I injected some BUGs in various places on 32-bit an 64-bit and it
seemed to do the right thing.  Depending on how early they were, I
either got a clean hang or I got a printout, and whether it displayed
anything didn't seem to change with and without the patches.  I think
that early_printk doesn't work from the very very beginning.

I also tried a bad wrmsrl at a couple early points.  Very very early
it just works with not warning.  A little later and it prints the
warning.

--Andy