AMD systems support zero CBM (capacity bit mask) for cache allocation.
That is reflected in rdt_init_res_defs_amd() by:
r->cache.arch_has_empty_bitmaps = true;
However given the unified code in cbm_validate(), checking for:
val == 0 && !arch_has_empty_bitmaps
is not enough because of another check in cbm_validate():
if ((zero_bit - first_bit) < r->cache.min_cbm_bits)
The default value of r->cache.min_cbm_bits = 1.
Leading to:
$ cd /sys/fs/resctrl
$ mkdir foo
$ cd foo
$ echo L3:0=0 > schemata
-bash: echo: write error: Invalid argument
$ cat /sys/fs/resctrl/info/last_cmd_status
Need at least 1 bits in the mask
Initialize the min_cbm_bits to 0 for AMD. Also, remove the default
setting of min_cbm_bits and initialize it separately.
After the fix:
$ cd /sys/fs/resctrl
$ mkdir foo
$ cd foo
$ echo L3:0=0 > schemata
$ cat /sys/fs/resctrl/info/last_cmd_status
ok
Fixes: 316e7f901f ("x86/resctrl: Add struct rdt_cache::arch_has_{sparse, empty}_bitmaps")
Co-developed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: James Morse <james.morse@arm.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/lkml/20220517001234.3137157-1-eranian@google.com
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