x86/resctrl: Add struct rdt_cache::arch_has_{sparse, empty}_bitmaps

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Intel CPUs expect the cache bitmap provided by user-space to have on a
single span of 1s, whereas AMD can support bitmaps like 0xf00f. Arm's
MPAM support also allows sparse bitmaps.

Similarly, Intel CPUs check at least one bit set, whereas AMD CPUs are
quite happy with an empty bitmap. Arm's MPAM allows an empty bitmap.

To move resctrl out to /fs/, platform differences like this need to be
explained.

Add two resource properties arch_has_{empty,sparse}_bitmaps. Test these
around the relevant parts of cbm_validate().

Merging the validate calls causes AMD to gain the min_cbm_bits test
needed for Haswell, but as it always sets this value to 1, it will never
match.

 [ bp: Massage commit message. ]

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lkml.kernel.org/r/20200708163929.2783-10-james.morse@arm.com

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James Morse 2020-07-08 16:39:28 +00:00 • committed by Borislav Petkov

parent 5df3ca9334

commit 316e7f901f

3 changed files with 22 additions and 39 deletions

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14

arch/x86/kernel/cpu/resctrl/core.c

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39

arch/x86/kernel/cpu/resctrl/ctrlmondata.c

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8

arch/x86/kernel/cpu/resctrl/internal.h

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