On Mon, Jun 01, 2026 at 08:23:46AM -0700, Dave Jiang wrote:
>
>
> On 5/29/26 11:40 PM, Anisa Su wrote:
> > On Wed, May 27, 2026 at 03:28:56PM -0700, Dave Jiang wrote:
> >>
> >>
> >> On 5/23/26 2:42 AM, Anisa Su wrote:
[snip]
> >>> + struct cxl_mbox_get_dc_config_out *dc_resp __free(kfree) =
> >>> + kmalloc(dc_resp_size, GFP_KERNEL);
> >>> + if (!dc_resp)
> >>> + return -ENOMEM;
> >>> +
> >>> + /**
> >>
> >> /*
> >>
> >>> + * Read and check all partition information for validity and potential
> >>> + * debugging; see debug output in cxl_dc_check()
> >>> + */
> >>> + start_partition = 0;
> >>> + num_partitions = 0;
> >>> + do {
> >>> + int rc, i, j;
> >>> +
> >>> + rc = cxl_get_dc_config(mbox, start_partition, dc_resp,
> >>> dc_resp_size);
> >>> + if (rc < 0) {
> >>> + dev_err(dev, "Failed to get DC config: %d\n", rc);
> >>> + return rc;
> >>> + }
> >>> +
> > if (rc == 0) {
> > dev_err(dev,
> > "Device reported %u partitions available but
> > returned none at index %u\n",
> > dc_resp->avail_partition_count,
> > start_partition);
> > return -EIO;
> > }
> >>> + num_partitions += rc;
> >>
> >> Would cxl_get_dc_config() keep returning 0 be a problem? Not likely to
> >> happen unless device is malicious.
> >>
> > Not sure but I added a check anyway. ^ See above. It prohibits
> > cxl_get_dc_config() returning 0 at all though. But could be changed to
> > err only if 0 partitions are returned X amount of times...?
>
> I think as long as we have a way to detect that we aren't moving forward in
> this loop and need to get out at some point.
>
> DJ
>
I'll keep the check above then, and just prohibit returning 0 partitions
when the device reports that it has more partitions available, since I don't
think it makes sense for the device to transiently return 0 and for some
reason make progress on retry anyway...
But need to move it below this check
if (num_partitions < 1 || num_partitions > CXL_MAX_DC_PARTITIONS) {
so the no forward progress check is differentiated from returning 0
partitions.
Thanks,
Anisa
> >>> +
> >>> + if (num_partitions < 1 || num_partitions >
> >>> CXL_MAX_DC_PARTITIONS) {
> >>> + dev_err(dev, "Invalid num of dynamic capacity
> >>> partitions %d\n",
> >>> + num_partitions);
> >>> + return -EINVAL;
> >>> + }
> >>> +
> >>> + for (i = start_partition, j = 0; i < num_partitions; i++, j++) {
> >>> + rc = cxl_dc_check(dev, partitions, i,
> >>> + &dc_resp->partition[j]);
> >>> + if (rc)
> >>> + return rc;
> >>> + }
> >>> +
> >>> + start_partition = num_partitions;
> >>> +
> >>> + } while (num_partitions < dc_resp->avail_partition_count);
> >>> +
> >>> + /* Return 1st partition */
> >>> + dc_info->start = partitions[0].start;
> >>> + dc_info->size = partitions[0].size;
> >>> + dev_dbg(dev, "Returning partition 0 %zu size %zu\n",
> >>> + dc_info->start, dc_info->size);
> >>> +
> >>> + return 0;
> >>> +}
> >>> +EXPORT_SYMBOL_NS_GPL(cxl_dev_dc_identify, "CXL");
> >>> +
>
[snip]
