cxl/core: Fix potential payload size confusion in cxl_mem_get_poison()

A recent change to cxl_mem_get_records_log() [1] highlighted a subtle
nuance of looping calls to cxl_internal_send_cmd(), i.e. that
cxl_internal_send_cmd() modifies the 'size_out' member of the @mbox_cmd
argument. That mechanism is useful for communicating underflow, but it
is unwanted when reusing @mbox_cmd for a subsequent submission. It turns
out that cxl_xfer_log() avoids this scenario by always redefining
@mbox_cmd each iteration.

Update cxl_mem_get_records_log() and cxl_mem_get_poison() to follow the
same style as cxl_xfer_log(), i.e. re-define @mbox_cmd each iteration.
The cxl_mem_get_records_log() change is just a style fixup, but the
cxl_mem_get_poison() change is a potential fix, per Alison [2]:

    Poison list retrieval can hit this case if the MORE flag is set and
    a follow on read of the list delivers more records than the previous
    read.  ie. device gives one record, sets the _MORE flag, then gives 5.

Not an urgent fix since this behavior has not been seen in the wild,
but worth tracking as a fix.

Cc: Kwangjin Ko <kwangjin.ko@sk.com>
Cc: Alison Schofield <alison.schofield@intel.com>
Fixes: ed83f7ca398b ("cxl/mbox: Add GET_POISON_LIST mailbox command")
Link: http://lore.kernel.org/r/20240402081404.1106-2-kwangjin.ko@sk.com
Link: http://lore.kernel.org/r/ZhAhAL/GOaWFrauw@aschofie-mobl2
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://lore.kernel.org/r/171235441633.2716581.12330082428680958635.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index f0f54aeccc872b50311a14958ddf874860af7982..65185c9fa00134e4ed9f5449628ae04f053ba927 100644 (file)
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -946,25 +946,22 @@ static void cxl_mem_get_records_log(struct cxl_memdev_state *mds,
        struct cxl_memdev *cxlmd = mds->cxlds.cxlmd;
        struct device *dev = mds->cxlds.dev;
        struct cxl_get_event_payload *payload;
-       struct cxl_mbox_cmd mbox_cmd;
        u8 log_type = type;
        u16 nr_rec;
 
        mutex_lock(&mds->event.log_lock);
        payload = mds->event.buf;
 
-       mbox_cmd = (struct cxl_mbox_cmd) {
-               .opcode = CXL_MBOX_OP_GET_EVENT_RECORD,
-               .payload_in = &log_type,
-               .size_in = sizeof(log_type),
-               .payload_out = payload,
-               .min_out = struct_size(payload, records, 0),
-       };
-
        do {
                int rc, i;
-
-               mbox_cmd.size_out = mds->payload_size;
+               struct cxl_mbox_cmd mbox_cmd = (struct cxl_mbox_cmd) {
+                       .opcode = CXL_MBOX_OP_GET_EVENT_RECORD,
+                       .payload_in = &log_type,
+                       .size_in = sizeof(log_type),
+                       .payload_out = payload,
+                       .size_out = mds->payload_size,
+                       .min_out = struct_size(payload, records, 0),
+               };
 
                rc = cxl_internal_send_cmd(mds, &mbox_cmd);
                if (rc) {
@@ -1297,7 +1294,6 @@ int cxl_mem_get_poison(struct cxl_memdev *cxlmd, u64 offset, u64 len,
        struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds);
        struct cxl_mbox_poison_out *po;
        struct cxl_mbox_poison_in pi;
-       struct cxl_mbox_cmd mbox_cmd;
        int nr_records = 0;
        int rc;
 
@@ -1309,16 +1305,16 @@ int cxl_mem_get_poison(struct cxl_memdev *cxlmd, u64 offset, u64 len,
        pi.offset = cpu_to_le64(offset);
        pi.length = cpu_to_le64(len / CXL_POISON_LEN_MULT);
 
-       mbox_cmd = (struct cxl_mbox_cmd) {
-               .opcode = CXL_MBOX_OP_GET_POISON,
-               .size_in = sizeof(pi),
-               .payload_in = &pi,
-               .size_out = mds->payload_size,
-               .payload_out = po,
-               .min_out = struct_size(po, record, 0),
-       };
-
        do {
+               struct cxl_mbox_cmd mbox_cmd = (struct cxl_mbox_cmd){
+                       .opcode = CXL_MBOX_OP_GET_POISON,
+                       .size_in = sizeof(pi),
+                       .payload_in = &pi,
+                       .size_out = mds->payload_size,
+                       .payload_out = po,
+                       .min_out = struct_size(po, record, 0),
+               };
+
                rc = cxl_internal_send_cmd(mds, &mbox_cmd);
                if (rc)
                        break;