x86, amd: Support L3 Cache Partitioning on AMD family 0x15 CPUs

L3 Cache Partitioning allows selecting which of the 4 L3 subcaches can be used
for evictions by the L2 cache of each compute unit. By writing a 4-bit
hexadecimal mask into the the sysfs file
/sys/devices/system/cpu/cpuX/cache/index3/subcaches, the user can set the
enabled subcaches for a CPU.

The settings are directly read from and written to the hardware, so there is no
way to have contradicting settings for two CPUs belonging to the same compute
unit. Writing will always overwrite any previous setting for a compute unit.

Signed-off-by: Hans Rosenfeld <hans.rosenfeld@amd.com>
Cc: <Andreas.Herrmann3@amd.com>
LKML-Reference: <1297098639-431383-1-git-send-email-hans.rosenfeld@amd.com>
[ -v3: minor style fixes ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 63 insertions, 0 deletions

diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index 4ae9a961c33c..bf79a4a6ee22 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -95,6 +95,10 @@ int amd_cache_northbridges(void)
 	if (boot_cpu_data.x86 == 0x15)
 		amd_northbridges.flags |= AMD_NB_L3_INDEX_DISABLE;
 
+	/* L3 cache partitioning is supported on family 0x15 */
+	if (boot_cpu_data.x86 == 0x15)
+		amd_northbridges.flags |= AMD_NB_L3_PARTITIONING;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(amd_cache_northbridges);
@@ -112,6 +116,65 @@ int __init early_is_amd_nb(u32 device)
 	return 0;
 }
 
+int amd_get_subcaches(int cpu)
+{
+	struct pci_dev *link = node_to_amd_nb(amd_get_nb_id(cpu))->link;
+	unsigned int mask;
+	int cuid = 0;
+
+	if (!amd_nb_has_feature(AMD_NB_L3_PARTITIONING))
+		return 0;
+
+	pci_read_config_dword(link, 0x1d4, &mask);
+
+#ifdef CONFIG_SMP
+	cuid = cpu_data(cpu).compute_unit_id;
+#endif
+	return (mask >> (4 * cuid)) & 0xf;
+}
+
+int amd_set_subcaches(int cpu, int mask)
+{
+	static unsigned int reset, ban;
+	struct amd_northbridge *nb = node_to_amd_nb(amd_get_nb_id(cpu));
+	unsigned int reg;
+	int cuid = 0;
+
+	if (!amd_nb_has_feature(AMD_NB_L3_PARTITIONING) || mask > 0xf)
+		return -EINVAL;
+
+	/* if necessary, collect reset state of L3 partitioning and BAN mode */
+	if (reset == 0) {
+		pci_read_config_dword(nb->link, 0x1d4, &reset);
+		pci_read_config_dword(nb->misc, 0x1b8, &ban);
+		ban &= 0x180000;
+	}
+
+	/* deactivate BAN mode if any subcaches are to be disabled */
+	if (mask != 0xf) {
+		pci_read_config_dword(nb->misc, 0x1b8, &reg);
+		pci_write_config_dword(nb->misc, 0x1b8, reg & ~0x180000);
+	}
+
+#ifdef CONFIG_SMP
+	cuid = cpu_data(cpu).compute_unit_id;
+#endif
+	mask <<= 4 * cuid;
+	mask |= (0xf ^ (1 << cuid)) << 26;
+
+	pci_write_config_dword(nb->link, 0x1d4, mask);
+
+	/* reset BAN mode if L3 partitioning returned to reset state */
+	pci_read_config_dword(nb->link, 0x1d4, &reg);
+	if (reg == reset) {
+		pci_read_config_dword(nb->misc, 0x1b8, &reg);
+		reg &= ~0x180000;
+		pci_write_config_dword(nb->misc, 0x1b8, reg | ban);
+	}
+
+	return 0;
+}
+
 int amd_cache_gart(void)
 {
        int i;