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xen-devel
[Xen-devel] Re: [PATCH RFC V4 09/10] x86/jump_label: use GENERIC_NOP5_AT
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To: |
"H. Peter Anvin" <hpa@xxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH RFC V4 09/10] x86/jump_label: use GENERIC_NOP5_ATOMIC instead of jmp5 +0 |
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From: |
Steven Rostedt <rostedt@xxxxxxxxxxx> |
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Date: |
Fri, 14 Oct 2011 20:22:20 -0400 |
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Cc: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, Jan Glauber <jang@xxxxxxxxxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Jason Baron <jbaron@xxxxxxxxxx>, David Daney <david.daney@xxxxxxxxxx>, Michael, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Ellerman <michael@xxxxxxxxxxxxxx>, Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx> |
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Fri, 14 Oct 2011 17:24:12 -0700 |
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<cover.1318464169.git.jeremy.fitzhardinge@xxxxxxxxxx> <34ede5db1571d541a5c3fc49923bb353a37dd431.1318464413.git.jeremy.fitzhardinge@xxxxxxxxxx> <4E97067A.2070305@xxxxxxxxx> <4E97188A.6040400@xxxxxxxx> <1318531022.12224.13.camel@xxxxxxxxxxxxxxxxxxx> <4E98AF71.40303@xxxxxxxxx> |
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On Fri, 2011-10-14 at 14:53 -0700, H. Peter Anvin wrote:
> On 10/13/2011 11:37 AM, Steven Rostedt wrote:
> > On Thu, 2011-10-13 at 09:57 -0700, Jeremy Fitzhardinge wrote:
> >> On 10/13/2011 08:40 AM, H. Peter Anvin wrote:
> >>> On 10/12/2011 05:08 PM, Jeremy Fitzhardinge wrote:
> >>>> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> >>>>
> >>>> GENERIC_NOP5_ATOMIC should make a better nop.
> >>>>
> >>> On 32 bits, yes. On 64 bits you should use P6_NOP5_ATOMIC.
> >>
> >> Something like this?
> >>
> >
> > No, we only care about 5byte nops here. Look at ideal_nop in
> > alterative.c
> >
>
> He needs a compile-time alternative.
I didn't explain this well. I actually just meant something like:
#ifdef CONFIG_X86_64
# define IDEAL_NOP5 P6_NOP5_ATOMIC
#else
# define IDEAL_NOP5 GENERIC_NOP5_ATOMIC
#endif
That is, we know we are using this for a 5byte jump. Just keep it simple
for that. Do you envision needing other nops too? Well, we could do 2
byte nops, but I think we could use the same for both. Can't we?
-- Steve
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