[RFC PATCH v2 1/4] cxl: Enable mailbox ops with background only if request abort operation is supported.

[Ravis OpenSrc <Ravis.OpenSrc@micron.com>]

Enabling mailbox commands only if background operation and
request abort cancellation are both supported.

This check is to allow user space commands to initiate
background commands responsibly while complying with any
default background timeout implemented in kernel.

Link:
https://lore.kernel.org/linux-cxl/66035c2e8ba17_770232948b@dwillia2-xfh.jf.intel.com.notmuch/

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ajay Joshi <ajay.opensrc@micron.com>
Signed-off-by: Ravi Shankar <ravis.opensrc@micron.com>
---
 drivers/cxl/core/mbox.c | 12 ++++++++++--
 drivers/cxl/cxlmem.h    | 16 ++++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 5175138c4fb7..8c0144913b9e 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -733,12 +733,20 @@ static void cxl_walk_cel(struct cxl_memdev_state *mds, size_t size, u8 *cel)
 
         for (i = 0; i < cel_entries; i++) {
                 u16 opcode = le16_to_cpu(cel_entry[i].opcode);
+               u16 effect = le16_to_cpu(cel_entry[i].effect);
                 struct cxl_mem_command *cmd = cxl_mem_find_command(opcode);
                 int enabled = 0;
 
                 if (cmd) {
-                       set_bit(cmd->info.id, mds->enabled_cmds);
-                       enabled++;
+                       /*
+                        * For background operation commands, enable only if
+                        * Request abort background operation is supported.
+                        */
+                       if (!(effect & CXL_CEL_FLAG_BACKGROUND_OPERATION) ||
+                          (effect & CXL_CEL_FLAG_REQ_ABORT_BACKGROUND_SUPPORTED)) {
+                               set_bit(cmd->info.id, mds->enabled_cmds);
+                               enabled++;
+                       }
                 }
 
                 if (cxl_is_poison_command(opcode)) {
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 2a25d1957ddb..d8c0894797ac 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -579,6 +579,22 @@ struct cxl_cel_entry {
         __le16 effect;
 } __packed;
 
+/*
+ * CEL Entry Effects
+ * CXL rev 3.1 Section 8.2.9.5.2.1; Table 8-75
+ */
+#define        CXL_CEL_FLAG_CFG_CHANGE_AFTER_RESET BIT(0)
+#define        CXL_CEL_FLAG_CFG_CHANGE_IMMEDIATE BIT(1)
+#define        CXL_CEL_FLAG_DATA_CHANGE_IMMEDIATE BIT(2)
+#define        CXL_CEL_FLAG_POLICY_CHANGE_IMMEDIATE BIT(3)
+#define        CXL_CEL_FLAG_LOG_CHANGE_IMMEDIATE BIT(4)
+#define        CXL_CEL_FLAG_SECURITY_CHANGE BIT(5)
+#define        CXL_CEL_FLAG_BACKGROUND_OPERATION BIT(6)
+#define        CXL_CEL_FLAG_SECONDARY_MAILBOX_SUPPORTED BIT(7)
+#define        CXL_CEL_FLAG_REQ_ABORT_BACKGROUND_SUPPORTED BIT(8)
+#define        CXL_CEL_FLAG_CFG_CHANGE_AFTER_CONV_RESET BIT(10)
+#define        CXL_CEL_FLAG_CFG_CHANGE_AFTER_CXL_RESET BIT(11)
+
 struct cxl_mbox_get_log {
         uuid_t uuid;
         __le32 offset;
-- 
2.43.0