"io_alloc" feature is a mechanism that enables direct insertion of data
from I/O devices into the L3 cache. By directly caching data from I/O
devices rather than first storing the I/O data in DRAM, it reduces the
demands on DRAM bandwidth and reduces latency to the processor consuming
the I/O data.
io_alloc feature uses the highest CLOSID to route the traffic from I/O
devices. Provide the interface to modify io_alloc CBMs (Capacity Bit Mask)
when feature is enabled.
Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v3: Minor changes due to changes in resctrl_arch_get_io_alloc_enabled()
and resctrl_io_alloc_closid_get().
Taken care of handling the CBM update when CDP is enabled.
Updated the commit log to make it generic.
v2: Added more generic text in documentation.
---
Documentation/arch/x86/resctrl.rst | 12 ++
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 2 +-
arch/x86/kernel/cpu/resctrl/internal.h | 1 +
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 134 +++++++++++++++++++++-
4 files changed, 147 insertions(+), 2 deletions(-)
diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 1b67e31d626c..29c8851bcc7f 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -169,6 +169,18 @@ related to allocation:
When CDP is enabled, io_alloc routes I/O traffic using the highest
CLOSID allocated for the instruction cache.
+"io_alloc_cbm":
+ Capacity Bit Masks (CBMs) available to supported IO devices which
+ can directly insert cache lines in L3 which can help to reduce the
+ latency. CBM can be configured by writing to the interface in the
+ following format::
+
+ L3:<cache_id0>=<cbm>;<cache_id1>=<cbm>;...
+
+ When CDP is enabled, L3 control is divided into two separate resources:
+ L3CODE and L3DATA. However, the CBM can only be updated on the L3CODE
+ resource.
+
Memory bandwidth(MB) subdirectory contains the following files
with respect to allocation:
diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index d272dea43924..4dfee0436c1c 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -102,7 +102,7 @@ int parse_bw(struct rdt_parse_data *data, struct resctrl_schema *s,
* requires at least two bits set.
* AMD allows non-contiguous bitmasks.
*/
-static bool cbm_validate(char *buf, u32 *data, struct rdt_resource *r)
+bool cbm_validate(char *buf, u32 *data, struct rdt_resource *r)
{
unsigned long first_bit, zero_bit, val;
unsigned int cbm_len = r->cache.cbm_len;
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 07cf8409174d..702f6926bbdf 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -669,4 +669,5 @@ void rdt_staged_configs_clear(void);
bool closid_allocated(unsigned int closid);
int resctrl_find_cleanest_closid(void);
void show_doms(struct seq_file *s, struct resctrl_schema *schema, int closid);
+bool cbm_validate(char *buf, u32 *data, struct rdt_resource *r);
#endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 81b9d8c5dabf..9997cbfc1c19 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1999,6 +1999,137 @@ static int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of,
return ret;
}
+/*
+ * Read the CBM and check the validity. Make sure CBM is not shared
+ * with any other exclusive resctrl groups.
+ */
+static int resctrl_io_alloc_parse_cbm(char *buf, struct resctrl_schema *s,
+ struct rdt_ctrl_domain *d)
+{
+ struct resctrl_staged_config *cfg;
+ struct rdt_resource *r = s->res;
+ u32 io_alloc_closid;
+ u32 cbm_val;
+
+ cfg = &d->staged_config[s->conf_type];
+ if (cfg->have_new_ctrl) {
+ rdt_last_cmd_printf("Duplicate domain %d\n", d->hdr.id);
+ return -EINVAL;
+ }
+
+ if (!cbm_validate(buf, &cbm_val, r))
+ return -EINVAL;
+
+ /*
+ * The CBM may not overlap with other exclusive group.
+ */
+ io_alloc_closid = resctrl_io_alloc_closid_get(r, s);
+ if (rdtgroup_cbm_overlaps(s, d, cbm_val, io_alloc_closid, true)) {
+ rdt_last_cmd_puts("Overlaps with exclusive group\n");
+ return -EINVAL;
+ }
+
+ cfg->new_ctrl = cbm_val;
+ cfg->have_new_ctrl = true;
+
+ return 0;
+}
+
+static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
+ struct resctrl_schema *s)
+{
+ struct rdt_ctrl_domain *d;
+ char *dom = NULL, *id;
+ unsigned long dom_id;
+
+next:
+ if (!line || line[0] == '\0')
+ return 0;
+
+ dom = strsep(&line, ";");
+ id = strsep(&dom, "=");
+ if (!dom || kstrtoul(id, 10, &dom_id)) {
+ rdt_last_cmd_puts("Missing '=' or non-numeric domain\n");
+ return -EINVAL;
+ }
+
+ dom = strim(dom);
+ list_for_each_entry(d, &r->ctrl_domains, hdr.list) {
+ if (d->hdr.id == dom_id) {
+ if (resctrl_io_alloc_parse_cbm(dom, s, d))
+ return -EINVAL;
+ goto next;
+ }
+ }
+ return -EINVAL;
+}
+
+static ssize_t resctrl_io_alloc_cbm_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct resctrl_schema *s = of->kn->parent->priv;
+ struct rdt_resource *r = s->res;
+ u32 io_alloc_closid;
+ char *resname;
+ int ret = 0;
+
+ /* Valid input requires a trailing newline */
+ if (nbytes == 0 || buf[nbytes - 1] != '\n')
+ return -EINVAL;
+
+ buf[nbytes - 1] = '\0';
+
+ if (!r->cache.io_alloc_capable || s->conf_type == CDP_DATA) {
+ rdt_last_cmd_puts("io_alloc feature is not supported on the resource\n");
+ return -EINVAL;
+ }
+
+ cpus_read_lock();
+ mutex_lock(&rdtgroup_mutex);
+
+ rdt_last_cmd_clear();
+ rdt_staged_configs_clear();
+
+ if (!resctrl_arch_get_io_alloc_enabled(r)) {
+ rdt_last_cmd_puts("io_alloc feature is not enabled\n");
+ ret = -EINVAL;
+ goto cbm_write_out;
+ }
+
+ resname = strim(strsep(&buf, ":"));
+ if (!buf) {
+ rdt_last_cmd_puts("Missing ':'\n");
+ ret = -EINVAL;
+ goto cbm_write_out;
+ }
+
+ if (strcmp(resname, s->name)) {
+ rdt_last_cmd_printf("Unsupported resource name '%s'\n", resname);
+ ret = -EINVAL;
+ goto cbm_write_out;
+ }
+
+ if (buf[0] == '\0') {
+ rdt_last_cmd_printf("Missing '%s' value\n", resname);
+ ret = -EINVAL;
+ goto cbm_write_out;
+ }
+
+ ret = resctrl_io_alloc_parse_line(buf, r, s);
+ if (ret)
+ goto cbm_write_out;
+
+ io_alloc_closid = resctrl_io_alloc_closid_get(r, s);
+ ret = resctrl_arch_update_domains(r, io_alloc_closid);
+
+cbm_write_out:
+ rdt_staged_configs_clear();
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+
+ return ret ?: nbytes;
+}
+
/* rdtgroup information files for one cache resource. */
static struct rftype res_common_files[] = {
{
@@ -2160,9 +2291,10 @@ static struct rftype res_common_files[] = {
},
{
.name = "io_alloc_cbm",
- .mode = 0444,
+ .mode = 0644,
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = resctrl_io_alloc_cbm_show,
+ .write = resctrl_io_alloc_cbm_write,
},
{
.name = "mba_MBps_event",
--
2.34.1
