[NDCTL PATCH v5 3/4] ndctl: cxl: add QoS class check for CXL region creation

[Dave Jiang]

The CFMWS provides a QTG ID. The kernel driver creates a root decoder that
represents the CFMWS. A qos_class attribute is exported via sysfs for the root
decoder.

One or more QoS class tokens are retrieved via QTG ID _DSM from the ACPI0017
device for a CXL memory device. The input for the _DSM is the read and write
latency and bandwidth for the path between the device and the CPU. The
numbers are constructed by the kernel driver for the _DSM input. When a
device is probed, QoS class tokens  are retrieved. This is useful for a
hot-plugged CXL memory device that does not have regions created.

Add a QoS check during region creation. Emit a warning if the qos_class
token from the root decoder is different than the mem device qos_class
token. User parameter options are provided to fail instead of just
warning.

Reviewed-by: Alison Schofield <alison.schofi...@intel.com>
Signed-off-by: Dave Jiang <dave.ji...@intel.com>
---
 Documentation/cxl/cxl-create-region.txt |  9 ++++
 cxl/region.c                            | 56 ++++++++++++++++++++++++-
 2 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/Documentation/cxl/cxl-create-region.txt 
b/Documentation/cxl/cxl-create-region.txt
index f11a412bddfe..d5e34cf38236 100644
--- a/Documentation/cxl/cxl-create-region.txt
+++ b/Documentation/cxl/cxl-create-region.txt
@@ -105,6 +105,15 @@ include::bus-option.txt[]
        supplied, the first cross-host bridge (if available), decoder that
        supports the largest interleave will be chosen.
 
+-e::
+--strict::
+       Enforce strict execution where any potential error will force failure.
+       For example, if qos_class mismatches region creation will fail.
+
+-q::
+--no-enforce-qos::
+       Parameter to bypass qos_class mismatch failure. Will only emit warning.
+
 include::human-option.txt[]
 
 include::debug-option.txt[]
diff --git a/cxl/region.c b/cxl/region.c
index 3a762db4800e..f9033fa0afbf 100644
--- a/cxl/region.c
+++ b/cxl/region.c
@@ -32,6 +32,8 @@ static struct region_params {
        bool force;
        bool human;
        bool debug;
+       bool strict;
+       bool no_qos;
 } param = {
        .ways = INT_MAX,
        .granularity = INT_MAX,
@@ -49,6 +51,8 @@ struct parsed_params {
        const char **argv;
        struct cxl_decoder *root_decoder;
        enum cxl_decoder_mode mode;
+       bool strict;
+       bool no_qos;
 };
 
 enum region_actions {
@@ -81,7 +85,9 @@ OPT_STRING('U', "uuid", &param.uuid, \
           "region uuid", "uuid for the new region (default: autogenerate)"), \
 OPT_BOOLEAN('m', "memdevs", &param.memdevs, \
            "non-option arguments are memdevs"), \
-OPT_BOOLEAN('u', "human", &param.human, "use human friendly number formats")
+OPT_BOOLEAN('u', "human", &param.human, "use human friendly number formats"), \
+OPT_BOOLEAN('e', "strict", &param.strict, "strict execution enforcement"), \
+OPT_BOOLEAN('q', "no-enforce-qos", &param.no_qos, "no enforce of qos_class")
 
 static const struct option create_options[] = {
        BASE_OPTIONS(),
@@ -360,6 +366,9 @@ static int parse_create_options(struct cxl_ctx *ctx, int 
count,
                }
        }
 
+       p->strict = param.strict;
+       p->no_qos = param.no_qos;
+
        return 0;
 
 err:
@@ -467,6 +476,49 @@ static void set_type_from_decoder(struct cxl_ctx *ctx, 
struct parsed_params *p)
                p->mode = CXL_DECODER_MODE_PMEM;
 }
 
+static int create_region_validate_qos_class(struct cxl_ctx *ctx,
+                                           struct parsed_params *p)
+{
+       int root_qos_class;
+       int qos_class;
+       int i;
+
+       root_qos_class = cxl_root_decoder_get_qos_class(p->root_decoder);
+       if (root_qos_class == CXL_QOS_CLASS_NONE)
+               return 0;
+
+       for (i = 0; i < p->ways; i++) {
+               struct json_object *jobj =
+                       json_object_array_get_idx(p->memdevs, i);
+               struct cxl_memdev *memdev = json_object_get_userdata(jobj);
+
+               if (p->mode == CXL_DECODER_MODE_RAM)
+                       qos_class = cxl_memdev_get_ram_qos_class(memdev);
+               else
+                       qos_class = cxl_memdev_get_pmem_qos_class(memdev);
+
+               /* No qos_class entries. Possibly no kernel support */
+               if (qos_class == CXL_QOS_CLASS_NONE)
+                       break;
+
+               if (qos_class != root_qos_class) {
+                       if (p->strict && !p->no_qos) {
+                               log_err(&rl, "%s QoS Class mismatches %s\n",
+                                       
cxl_decoder_get_devname(p->root_decoder),
+                                       cxl_memdev_get_devname(memdev));
+
+                               return -ENXIO;
+                       }
+
+                       log_notice(&rl, "%s QoS Class mismatches %s\n",
+                                  cxl_decoder_get_devname(p->root_decoder),
+                                  cxl_memdev_get_devname(memdev));
+               }
+       }
+
+       return 0;
+}
+
 static int create_region_validate_config(struct cxl_ctx *ctx,
                                         struct parsed_params *p)
 {
@@ -507,6 +559,8 @@ found:
                return rc;
 
        collect_minsize(ctx, p);
+       create_region_validate_qos_class(ctx, p);
+
        return 0;
 }
 
-- 
2.43.0