Messages in this thread | | | Subject | Re: [PATCH v5 12/18] x86/split_lock: Enable #AC for split lock by default | From | Dave Hansen <> | Date | Tue, 12 Mar 2019 16:43:25 -0700 |
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On 3/12/19 4:00 PM, Fenghua Yu wrote: > Split locked access locks bus and degradates overall memory access
Either "split locked accesses lock" or "A split lock access locks".
s/degradates/degrades/
> performance. When split lock detection feature is enumerated, we want to
^ the
Also, you need to go back and remove all the "we"'s. Our friendly x86 maintainers prefer phrasing this like:
When split lock detection feature is enumerated, enable the feature...
> enable the feature by default to find any split lock issue and then fix > the issue.
Generally, the changelogs here are passable but pretty rough. They have a ton of issues like this and I'm sure they can be improved. I'm sure that with some love an attention they can be brought up to the highest standards.
> +#define DISABLE_SPLIT_LOCK_DETECT 0 > +#define ENABLE_SPLIT_LOCK_DETECT 1
These are a bit overkill, but oh well.
> +static int split_lock_detect_val; > + > /* > * Just in case our CPU detection goes bad, or you have a weird system, > * allow a way to override the automatic disabling of MPX. > @@ -161,10 +166,35 @@ static bool bad_spectre_microcode(struct cpuinfo_x86 *c) > return false; > } > > +static u32 new_sp_test_ctl_val(u32 test_ctl_val) > +{ > + /* Change the split lock setting. */ > + if (split_lock_detect_val == DISABLE_SPLIT_LOCK_DETECT) > + test_ctl_val &= ~TEST_CTL_ENABLE_SPLIT_LOCK_DETECT; > + else > + test_ctl_val |= TEST_CTL_ENABLE_SPLIT_LOCK_DETECT; > + > + return test_ctl_val; > +} > + > +static void init_split_lock_detect(struct cpuinfo_x86 *c) > +{ > + if (cpu_has(c, X86_FEATURE_SPLIT_LOCK_DETECT)) { > + u32 l, h; > + > + rdmsr(MSR_TEST_CTL, l, h); > + l = new_sp_test_ctl_val(l); > + wrmsr(MSR_TEST_CTL, l, h); > + pr_info_once("#AC for split lock is enabled\n"); > + } > +}
Please make sure you've removed all the "#AC for split lock" nomenclature in these patches. It's acronym nonsense and there's no reason to be so oblique. Just say "split lock detection enabled". This also needs a proper prefix, like "x86/intel:". Look around for examples.
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