x86/resctrl: Fix min_cbm_bits for AMD

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: 316e7f901f5a ("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

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index de62b0b..3266ea3 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -66,9 +66,6 @@ struct rdt_hw_resource rdt_resources_all[] = {
                        .rid                    = RDT_RESOURCE_L3,
                        .name                   = "L3",
                        .cache_level            = 3,
-                       .cache = {
-                               .min_cbm_bits   = 1,
-                       },
                        .domains                = domain_init(RDT_RESOURCE_L3),
                        .parse_ctrlval          = parse_cbm,
                        .format_str             = "%d=%0*x",
@@ -83,9 +80,6 @@ struct rdt_hw_resource rdt_resources_all[] = {
                        .rid                    = RDT_RESOURCE_L2,
                        .name                   = "L2",
                        .cache_level            = 2,
-                       .cache = {
-                               .min_cbm_bits   = 1,
-                       },
                        .domains                = domain_init(RDT_RESOURCE_L2),
                        .parse_ctrlval          = parse_cbm,
                        .format_str             = "%d=%0*x",
@@ -836,6 +830,7 @@ static __init void rdt_init_res_defs_intel(void)
                        r->cache.arch_has_sparse_bitmaps = false;
                        r->cache.arch_has_empty_bitmaps = false;
                        r->cache.arch_has_per_cpu_cfg = false;
+                       r->cache.min_cbm_bits = 1;
                } else if (r->rid == RDT_RESOURCE_MBA) {
                        hw_res->msr_base = MSR_IA32_MBA_THRTL_BASE;
                        hw_res->msr_update = mba_wrmsr_intel;
@@ -856,6 +851,7 @@ static __init void rdt_init_res_defs_amd(void)
                        r->cache.arch_has_sparse_bitmaps = true;
                        r->cache.arch_has_empty_bitmaps = true;
                        r->cache.arch_has_per_cpu_cfg = true;
+                       r->cache.min_cbm_bits = 0;
                } else if (r->rid == RDT_RESOURCE_MBA) {
                        hw_res->msr_base = MSR_IA32_MBA_BW_BASE;
                        hw_res->msr_update = mba_wrmsr_amd;