x86/resctrl: Allocate the cleanest CLOSID by searching closid_num_dirty_rmid

MPAM's PMG bits extend its PARTID space, meaning the same PMG value can be used
for different control groups.

This means once a CLOSID is allocated, all its monitoring ids may still be
dirty, and held in limbo.

Instead of allocating the first free CLOSID, on architectures where
CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID is enabled, search
closid_num_dirty_rmid[] to find the cleanest CLOSID.

The CLOSID found is returned to closid_alloc() for the free list
to be updated.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Link: https://lore.kernel.org/r/20240213184438.16675-11-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 872ba1a341039cfc5d1633517acc82291646d404..b7b9d9230bef0c83ae72b323ea37cefd49c26496 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -566,5 +566,7 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
 void __init thread_throttle_mode_init(void);
 void __init mbm_config_rftype_init(const char *config);
 void rdt_staged_configs_clear(void);
+bool closid_allocated(unsigned int closid);
+int resctrl_find_cleanest_closid(void);
 
 #endif /* _ASM_X86_RESCTRL_INTERNAL_H */

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 13b0c8d14f3de90bc637d611b47e6f123faa5e70..101f1b112d170323c078965a4b9845ce3a060d56 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -386,6 +386,51 @@ static struct rmid_entry *resctrl_find_free_rmid(u32 closid)
        return ERR_PTR(-ENOSPC);
 }
 
+/**
+ * resctrl_find_cleanest_closid() - Find a CLOSID where all the associated
+ *                                  RMID are clean, or the CLOSID that has
+ *                                  the most clean RMID.
+ *
+ * MPAM's equivalent of RMID are per-CLOSID, meaning a freshly allocated CLOSID
+ * may not be able to allocate clean RMID. To avoid this the allocator will
+ * choose the CLOSID with the most clean RMID.
+ *
+ * When the CLOSID and RMID are independent numbers, the first free CLOSID will
+ * be returned.
+ */
+int resctrl_find_cleanest_closid(void)
+{
+       u32 cleanest_closid = ~0;
+       int i = 0;
+
+       lockdep_assert_held(&rdtgroup_mutex);
+
+       if (!IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID))
+               return -EIO;
+
+       for (i = 0; i < closids_supported(); i++) {
+               int num_dirty;
+
+               if (closid_allocated(i))
+                       continue;
+
+               num_dirty = closid_num_dirty_rmid[i];
+               if (num_dirty == 0)
+                       return i;
+
+               if (cleanest_closid == ~0)
+                       cleanest_closid = i;
+
+               if (num_dirty < closid_num_dirty_rmid[cleanest_closid])
+                       cleanest_closid = i;
+       }
+
+       if (cleanest_closid == ~0)
+               return -ENOSPC;
+
+       return cleanest_closid;
+}
+
 /*
  * For MPAM the RMID value is not unique, and has to be considered with
  * the CLOSID. The (CLOSID, RMID) pair is allocated on all domains, which

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index bc6e0f83c847213581ca8bd78aee0718d64c1d24..8fc46204a6ccd2a86a69f8913dfe6b4bae90b3b3 100644 (file)
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -137,13 +137,22 @@ static void closid_init(void)
 
 static int closid_alloc(void)
 {
-       u32 closid = ffs(closid_free_map);
+       int cleanest_closid;
+       u32 closid;
 
        lockdep_assert_held(&rdtgroup_mutex);
 
-       if (closid == 0)
-               return -ENOSPC;
-       closid--;
+       if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID)) {
+               cleanest_closid = resctrl_find_cleanest_closid();
+               if (cleanest_closid < 0)
+                       return cleanest_closid;
+               closid = cleanest_closid;
+       } else {
+               closid = ffs(closid_free_map);
+               if (closid == 0)
+                       return -ENOSPC;
+               closid--;
+       }
        __clear_bit(closid, &closid_free_map);
 
        return closid;
@@ -163,7 +172,7 @@ void closid_free(int closid)
  * Return: true if @closid is currently associated with a resource group,
  * false if @closid is free
  */
-static bool closid_allocated(unsigned int closid)
+bool closid_allocated(unsigned int closid)
 {
        lockdep_assert_held(&rdtgroup_mutex);