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SubjectRe: [RFC patch] Immediate Values - x86 Optimization NMI and MCE support
Mathieu Desnoyers wrote:
> [Ingo: this patch is for RFC only. Do not merge.]
> * Peter Zijlstra ( wrote:
>> On Thu, 2009-09-24 at 11:03 -0400, Mathieu Desnoyers wrote:
>>> * Peter Zijlstra ( wrote:
>>>> On Thu, 2009-09-24 at 09:26 -0400, Mathieu Desnoyers wrote:
>>>>> plain text document attachment (tracepoints-immediate-values.patch)
>>>>> Use immediate values in tracepoints.
>>>> I might have missed it, but did both the Intel and AMD cpu folks clear
>>>> the SMP code rewrite bits?
>>> SMP handling is performed with stop_machine() in this patchset. Nothing
>>> fancy here.
>>> I've got other patches, not included in this patchset, which implements
>>> nmi-safe code modification, based on a scheme using breakpoints and
>>> IPIs, inspired from djprobes. That one might be worth clearing with
>>> intel/amd devs before merging.
>>> However, doing code patching within stop_machine() is pretty safe, given
>>> all other CPUs are busy-looping with interrupts off while this happens.
>>> Ftrace already does this.
>> Agreed, I missed this relied on stopmachine. No problem then.
>> It would be good to reduce reliance on stopmachine, so it would be good
>> to get some CPU folks looking at your alternative implementation.
>> Thanks!
> Sure, here is the patch applying on top of the immediate values
> patchset. It implements the breakpoint-based instruction patching
> scheme. I just provide this one for review. There is a following patch
> which makes the immediate values infrastructure use this arch-specific
> file, which I'll leave out for now.

Mathieu, could you check my previous patch?

I think we can share some code and ideas about generic XMC:-).
But since it seems that the imv requires a dedicated method,
I don't think we can share the code entirely. :-)

> +#include <asm/cacheflush.h>
> +
> +#define NR_NOPS 10

Why don't you reuse macros in asm/include/kprobes.h? :)

Thank you,

Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division


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