Messages in this thread |  | | Date | Sat, 9 Nov 2013 16:54:28 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/3] perf/x86/amd: AMD support for bp_len > HW_BREAKPOINT_LEN_8 |
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Just in case let me repeat, I can be easily wrong because I forgot how this series actually look and I don't have the patches now ;)
On 11/09, Frederic Weisbecker wrote: > > On Sat, Nov 09, 2013 at 04:11:56PM +0100, Oleg Nesterov wrote: > > On 11/08, Frederic Weisbecker wrote: > > > > > > > > > Does this feature only work on data breakpoint or is instruction breakpoint > > > address range supported as well? > > > > IIRC, execute range is supported as well. > > > > But. I can't look at the code now, but iirc this can't really work until > > we fix the (already discussed) problems with bp_len && X86_BREAKPOINT_LEN_X. > > IOW, we should not blame these patches if it doesn't work. > > Yeah, don't worry I don't plan to push back these patches for the sake of that bug, > that would be definetly unfair, especially as I introduced that issue :) > > And the patchset looks good overall, except for a few details but it's mostly ok,
OK,
> I just would like to fix that issue along the way. It would be really nice if we can > avoid having a mask _and_ a len for breakpoints.
Up to you and Suravee, but can't we cleanup this later?
This series was updated many times to address a lot of (sometimes contradictory) complaints.
> I mean, that doesn't look right to me, > it's two units basically measuring the same thing, so that's asking for conflicting troubles.
Yes. And we can kill either _len or _mask, not sure what would be more clean.
At least with the current implementation (again, iirc) mask == len -1. Although amd supports the more generic masks (but I can't recall the details).
> I'm just not sure how to reuse the len to express breakpoint ranges (that was in fact the > initial purpose of it) without breaking the tools.
Confused... user-space still uses len to express the range? Just the kernel "switches" to mask if len > 8 ?
Oleg.
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