linux-kernel - Re: [PATCH v2 1/2] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on

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Message-ID: <55FFF7B3.5010608@redhat.com>
Date:	Mon, 21 Sep 2015 14:27:31 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...capital.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	xen-devel <Xen-devel@...ts.xen.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KVM list <kvm@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2 1/2] x86/msr: Carry on after a non-"safe" MSR access
 fails without !panic_on_oops



On 21/09/2015 10:46, Ingo Molnar wrote:
> Or we could extend exception table entry encoding to include a 'warning bit', to 
> not bloat the kernel. If the exception handler code encounters such an exception 
> it would generate a one-time warning for that entry, but otherwise not crash the 
> kernel and continue execution with an all-zeroes result for the MSR read.

The 'warning bit' already exists, it is the opcode that caused the fault. :)

The concern about bloat is a good one.  However, why is it necessary to
keep native_*_msr* inline?  If they are moved out-of-line, using the
exception table becomes the obvious solution and doesn't cause bloat
anymore.

Paolo
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