Hi Babu, On 9/7/2022 10:59 AM, Babu Moger wrote: > AMD systems support zero CBM (capacity bit mask) for L3 allocation. Above mentions "for L3 allocation", but the change impacts L3 as well as L2 allocation. Perhaps just "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 > > Fix the issue by initializing 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 > > Link: https://lore.kernel.org/lkml/20220517001234.3137157-1-eranian@xxxxxxxxxx/ > Fixes: 316e7f901f5a ("x86/resctrl: Add struct rdt_cache::arch_has_{sparse, empty}_bitmaps") > Signed-off-by: Stephane Eranian <eranian@xxxxxxxxxx> > Signed-off-by: Babu Moger <babu.moger@xxxxxxx> > Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx> (apart from the changelog nitpick) Thank you for clarifying the way forward for this fix. Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx> Reinette
