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Message-ID: <CA+55aFwqq+TNB2vFV6=NENj6XHQMsWhw7qYWt1pBwX+Sdxn8kw@mail.gmail.com>
Date: Mon, 21 Sep 2015 10:27:49 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Ingo Molnar <mingo@...nel.org>,
Andy Lutomirski <luto@...capital.net>,
Thomas Gleixner <tglx@...utronix.de>,
Paolo Bonzini <pbonzini@...hat.com>,
xen-devel <Xen-devel@...ts.xen.org>,
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 9:49 AM, Arjan van de Ven <arjan@...ux.intel.com> wrote:
>>
>> How many msr reads are <i>so</i> critical that the function call
>> overhead would matter?
>
> if anything qualifies it'd be switch_to() and friends.
Is there anything else than the FS/GS_BASE thing (possibly hidden
behind inlines etc that I didn't get from a quick grep)? And why is
that sometimes using the "safe" version (in do_arch_prctl()), and
sometimes not (switch_to())?
I'm not convinced that mess is a good argument for the status quo ;)
> note that I'm not entirely happy about the notion of "safe" MSRs.
> They're safe as in "won't fault".
I wouldn't object to renaming them.
Linus
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