linux-kernel - Re: [PATCH v4 2/5] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on

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Message-ID: <20160314201826.GQ6344@twins.programming.kicks-ass.net>
Date:	Mon, 14 Mar 2016 21:18:26 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	xen-devel <Xen-devel@...ts.xen.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KVM list <kvm@...r.kernel.org>,
	Andy Lutomirski <luto@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/5] x86/msr: Carry on after a non-"safe" MSR access
 fails without !panic_on_oops

On Mon, Mar 14, 2016 at 11:10:16AM -0700, Andy Lutomirski wrote:
> A couple of the wrmsr users actually care about performance.  These
> are the ones involved in context switching and, to a lesser extent, in
> switching in and out of guest mode.

Right, this very much includes a number of perf MSRs. Some of those get
called from the context switch path, others from the NMI handler.