linux-kernel - Re: [PATCH v5 0/9] Improve non-"safe" MSR access failure handling

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Date:	Sat, 2 Apr 2016 08:13:36 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andy Lutomirski <luto@...nel.org>, X86 ML <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 Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v5 0/9] Improve non-"safe" MSR access failure handling

On Sat, Apr 2, 2016 at 7:24 AM, Linus Torvalds
<torvalds@...ux-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