On Tue, 1 Apr 2025 21:59:20 -0400 Gregory Price <[email protected]> wrote:
> Device capacity intended for use as system ram should be aligned to the > archite-defined memory block size or that capacity will be silently archite? > truncated and capacity stranded. > > As hotplug dax memory becomes more prevelant, the memory block size > alignment becomes more important for platform and device vendors to > pay attention to - so this truncation should not be silent. > > This issue is particularly relevant for CXL Dynamic Capacity devices, > whose capacity may arrive in spec-aligned but block-misaligned chunks. > > Suggested-by: David Hildenbrand <[email protected]> > Suggested-by: Dan Williams <[email protected]> > Signed-off-by: Gregory Price <[email protected]> One trivial comment inline otherwise seems reasonable to me. Reviewed-by: Jonathan Cameron <[email protected]> > --- > drivers/dax/kmem.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c > index e97d47f42ee2..32fe3215e11e 100644 > --- a/drivers/dax/kmem.c > +++ b/drivers/dax/kmem.c > @@ -13,6 +13,7 @@ > #include <linux/mman.h> > #include <linux/memory-tiers.h> > #include <linux/memory_hotplug.h> > +#include <linux/string_helpers.h> > #include "dax-private.h" > #include "bus.h" > > @@ -68,7 +69,7 @@ static void kmem_put_memory_types(void) > static int dev_dax_kmem_probe(struct dev_dax *dev_dax) > { > struct device *dev = &dev_dax->dev; > - unsigned long total_len = 0; > + unsigned long total_len = 0, orig_len = 0; > struct dax_kmem_data *data; > struct memory_dev_type *mtype; > int i, rc, mapped = 0; > @@ -97,6 +98,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) > for (i = 0; i < dev_dax->nr_range; i++) { > struct range range; > > + orig_len += range_len(&dev_dax->ranges[i].range); > rc = dax_kmem_range(dev_dax, i, &range); > if (rc) { > dev_info(dev, "mapping%d: %#llx-%#llx too small after > alignment\n", > @@ -109,6 +111,12 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) > if (!total_len) { > dev_warn(dev, "rejecting DAX region without any memory after > alignment\n"); > return -EINVAL; > + } else if (total_len != orig_len) { > + char buf[16]; > + > + string_get_size((orig_len - total_len), 1, STRING_UNITS_2, Trivial but do those inner brackets really add anything? > + buf, sizeof(buf)); > + dev_warn(dev, "DAX region truncated by %s due to alignment\n", > buf); > } > > init_node_memory_type(numa_node, mtype);
