Messages in this thread | | | Subject | Re: [PATCH v2 1/2] x86/msr: Carry on after a non-"safe" MSR access fails without !panic_on_oops | From | Arjan van de Ven <> | Date | Mon, 21 Sep 2015 09:49:10 -0700 |
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On 9/21/2015 9:36 AM, Linus Torvalds wrote: > On Mon, Sep 21, 2015 at 1:46 AM, Ingo Molnar <mingo@kernel.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?
if anything qualifies it'd be switch_to() and friends.
note that I'm not entirely happy about the notion of "safe" MSRs. They're safe as in "won't fault". Reading random MSRs isn't a generic safe operation though, but the name sort of gives people the impression that it is. Even with _safe variants, you still need to KNOW the MSR exists (by means of CPUID or similar) unfortunately.
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