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: <CA+55aFzKCi6pf0RP8HjDQYDsms6reB5AihuCAHEkVJtoOHk_Yw@mail.gmail.com>
Date:	Mon, 21 Sep 2015 09:36:15 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paolo Bonzini <pbonzini@...hat.com>,
	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 Mon, Sep 21, 2015 at 1:46 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> Linus, what's your preference?

So quite frankly, is there any reason we don't just implement
native_read_msr() as just

   unsigned long long native_read_msr(unsigned int msr)
   {
      int err;
      unsigned long long val;

      val = native_read_msr_safe(msr, &err);
      WARN_ON_ONCE(err);
      return val;
   }

Note: no inline, no nothing. Just put it in arch/x86/lib/msr.c, and be
done with it. I don't see the downside.

How many msr reads are <i>so</i> critical that the function call
overhead would matter? Get rid of the inline version of the _safe()
thing too, and put that thing there too.

                  Linus
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