Messages in this thread | | | Date | Tue, 10 Dec 2013 17:30:53 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 1/3] perf/x86/amd: AMD support for bp_len > HW_BREAKPOINT_LEN_8 |
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On Tue, Dec 10, 2013 at 05:19:45PM +0100, Oleg Nesterov wrote: > On 12/10, Frederic Weisbecker wrote: > > > > On Wed, Oct 02, 2013 at 11:11:06AM -0500, suravee.suthikulpanit@amd.com wrote: > > > @@ -279,7 +260,16 @@ static int arch_build_bp_info(struct perf_event *bp) > > > } > > > > > > /* Len */ > > > + info->mask = 0; > > > + > > > switch (bp->attr.bp_len) { > > > + default: > > > + if (!is_power_of_2(bp->attr.bp_len)) > > > + return -EINVAL; > > > + if (!cpu_has_bpext) > > > + return -EOPNOTSUPP; > > > + info->mask = bp->attr.bp_len - 1; > > > + /* fall through */ > > > > So, that's perhaps just personal preference but having the default on > > top of the switch makes things very confusing. Can't we put the above > > in the end of the switch instead? > > Then "fall through" won't work ;)
Indeed, now may be that's just me but it's very hard to parse :)
There are other ways to perform the above, it's no big deal if we duplicate one line of code.
> > > > @@ -314,11 +303,11 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp) > > > if (ret) > > > return ret; > > > > > > - ret = -EINVAL; > > > - > > > switch (info->len) { > > > case X86_BREAKPOINT_LEN_1: > > > align = 0; > > > + if (info->mask) > > > + align = info->mask; > > > > Confused, I thought mask is set only when length is above 8? > > Yes. But we need the info->len for hw anyway. if mask != 0 then > len == X86_BREAKPOINT_LEN_1 and it is still used by encode_dr7(). > Note that it is not the length in bytes, it is the magic x86 code.
Good point, and that matches the above fallthrough.
Thanks.
> > ->bp_len is the length. > > Oleg. >
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