On Mon, 2015-05-11 at 22:18 +0200, Borislav Petkov wrote: > 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. I will clarify the comment as follows. === uniform - Set to 1 when the region is not covered with multiple memory types by MTRRs. It is set for any return value. NOTE: The current code sets 'uniform' to 1 when the region is fully covered by a single MTRR entry or fully uncovered. However, it does not detect a uniform case that the region is covered by the same type but spanning multiple MTRR entries for simplicity. === > > 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. MTRRs disabled is not an error case as it could be a normal configuration on some platforms / BIOS setups. I clarified it in the above comment that uniform is set for any return value. > > 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. OK, I will change it to pr_warn_once(). Thanks, -Toshi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>