On 6/25/26 4:04 AM, Anisa Su wrote:
> From: Ira Weiny <[email protected]>
>
> Add an alignment gate to cxl_add_pending(): every extent in a tag group
> must have its start_dpa and length aligned to the dax region's mapping
> granularity. A misaligned extent makes the resulting dax device unusable,
> so drop the whole group rather than accept a partial allocation that would
> surface a broken dax_resource.
>
> Based on patches by John Groves.
>
> Signed-off-by: Ira Weiny <[email protected]>
> Signed-off-by: John Groves <[email protected]>
> Signed-off-by: Anisa Su <[email protected]>
Reviewed-by: Dave Jiang <[email protected]>
>
> ---
> Changes:
> [anisa: gate on the dax region's actual mapping alignment (PMD_SIZE)
> instead of a hardcoded SZ_2M]
> ---
> drivers/cxl/core/mbox.c | 51 +++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 49 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 08f51b8807c0..14ba263044f0 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -7,6 +7,8 @@
> #include <linux/unaligned.h>
> #include <linux/list.h>
> #include <linux/list_sort.h>
> +#include <linux/pgtable.h>
> +#include <linux/sizes.h>
> #include <cxlpci.h>
> #include <cxlmem.h>
> #include <cxl.h>
> @@ -1295,6 +1297,19 @@ static int add_to_pending_list(struct list_head
> *pending_list,
> return 0;
> }
>
> +/*
> + * Extents need to be aligned to dax region's mapping granularity.
> + * Use PMD_SIZE, since cxl_dax_region_probe() calls alloc_dax_region with
> + * PMD_SIZE for the 'align' parameter.
> + */
> +static bool cxl_extent_dcd_aligned(const struct cxl_extent *extent)
> +{
> + u64 start = le64_to_cpu(extent->start_dpa);
> + u64 len = le64_to_cpu(extent->length);
> +
> + return IS_ALIGNED(start, PMD_SIZE) && IS_ALIGNED(len, PMD_SIZE);
> +}
> +
> /*
> * Compare two extents by shared_extn_seq (ascending). list_sort is
> * stable, so extents with equal keys keep their arrival order from
> @@ -1395,11 +1410,38 @@ static int cxl_realize_group(struct cxl_memdev_state
> *mds, const uuid_t *tag,
> return group_cnt;
> }
>
> +/*
> + * Validate a tag @group before realizing it. Returns 0 if the group may be
> + * added, or a negative errno if it must be dropped. Further gates layer in
> + * here in later commits.
> + */
> +static int cxl_validate_group(struct cxl_memdev_state *mds, const uuid_t
> *tag,
> + struct list_head *group)
> +{
> + struct device *dev = mds->cxlds.dev;
> + struct cxl_extent_list_node *pos;
> +
> + /* Alignment gate — drop the group if any member fails */
> + list_for_each_entry(pos, group, list) {
> + if (!cxl_extent_dcd_aligned(pos->extent)) {
> + dev_warn(dev,
> + "Tag %pUb: dropping group, extent DPA:%#llx
> LEN:%#llx not %#llx-aligned\n",
> + tag,
> + le64_to_cpu(pos->extent->start_dpa),
> + le64_to_cpu(pos->extent->length),
> + (u64)PMD_SIZE);
> + return -EINVAL;
> + }
> + }
> +
> + return 0;
> +}
> +
> /*
> * Drive the pending Add-Capacity records through cxl_realize_group(),
> * grouped by tag. Per group: extract from pending, stable-sort by
> - * shared_extn_seq, realize the group, and on success move it onto the
> - * accepted list. Validation gates layer onto this loop in later commits.
> + * shared_extn_seq, validate, realize the group, and on success move it onto
> + * the accepted list.
> */
> static int cxl_add_pending(struct cxl_memdev_state *mds, bool existing)
> {
> @@ -1425,6 +1467,11 @@ static int cxl_add_pending(struct cxl_memdev_state
> *mds, bool existing)
> */
> list_sort(NULL, &group, extent_seq_compare);
>
> + if (cxl_validate_group(mds, &tag, &group)) {
> + drop_extent_group(&group);
> + continue;
> + }
> +
> cnt = cxl_realize_group(mds, &tag, &group, existing);
> if (cnt < 0) {
> drop_extent_group(&group);
