Messages in this thread | | | Date | Mon, 11 May 2015 22:18:27 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v4 7/7] mtrr, mm, x86: Enhance MTRR checks for KVA huge page mapping |
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On Mon, May 11, 2015 at 01:25:16PM -0600, Toshi Kani wrote: > > > @@ -235,13 +240,19 @@ static u8 mtrr_type_lookup_variable(u64 start, u64 end, u64 *partial_end, > > > * Return Values: > > > * MTRR_TYPE_(type) - The effective MTRR type for the region > > > * MTRR_TYPE_INVALID - MTRR is disabled > > > + * > > > + * Output Argument: > > > + * uniform - Set to 1 when MTRR covers the region uniformly, i.e. the region > > > + * is fully covered by a single MTRR entry or the default type. > > > > I'd call this "single_mtrr". "uniform" could also mean that the resulting > > type is uniform, i.e. of the same type but spanning multiple MTRRs. > > Actually, that is the intend of "uniform" and the same type but spanning > multiple MTRRs should set "uniform" to 1. The patch does not check such
So why does it say "is fully covered by a single MTRR entry or the default type." - the stress being on *single*
You need to make up your mind.
> We need to set "uniform" to 1 when MTRRs are disabled since there is no > type conflict with MTRRs.
No, this is wrong.
When we return an *error*, "uniform" should be *undefined* because MTRRs are disabled and callers should be checking whether it returned an error first and only *then* look at uniform.
> The warning was suggested by reviewers in the previous review so that > driver writers will notice the issue.
No, we don't flood dmesg so that driver writers notice stuff. We better fix the callers.
> Returning 0 here will lead > ioremap() to use 4KB mappings, but does not cause ioremap() to fail.
I guess a pr_warn_once() should be better then. Flooding dmesg with error messages for which the user can't really do anything about doesn't bring us anything.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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