在 2024/1/27 1:42, Jonathan Cameron 写道:
On Wed, 24 Jan 2024 17:15:26 +0800
Quanquan Cao <[email protected]> wrote:
Creating a region with 16 memory devices caused a problem. The div_u64_rem
function, used for dividing an unsigned 64-bit number by a 32-bit one,
faced an issue when SZ_256M * p->interleave_ways. The result surpassed
the maximum limit of the 32-bit divisor (4G), leading to an overflow
and a remainder of 0.
note: At this point, p->interleave_ways is 16, meaning 16 * 256M = 4G
To fix this issue, I replaced the div_u64_rem function with div64_u64_rem
and adjusted the type of the remainder.
Signed-off-by: Quanquan Cao <[email protected]>
Good find, though now I'm curious on whether you have a real system doing
16 way interleave :)
Yes, currently the specification is 8, and 16 will be the maximum value.
Reviewed-by: Jonathan Cameron <[email protected]>
---
drivers/cxl/core/region.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 0f05692bfec3..ce0e2d82bb2b 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -525,7 +525,7 @@ static int alloc_hpa(struct cxl_region *cxlr,
resource_size_t size)
struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
struct cxl_region_params *p = &cxlr->params;
struct resource *res;
- u32 remainder = 0;
+ u64 remainder = 0;
lockdep_assert_held_write(&cxl_region_rwsem);
@@ -545,7 +545,7 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size)
(cxlr->mode == CXL_DECODER_PMEM && uuid_is_null(&p->uuid)))
return -ENXIO;
- div_u64_rem(size, SZ_256M * p->interleave_ways, &remainder);
+ div64_u64_rem(size, (u64)SZ_256M * p->interleave_ways, &remainder);
if (remainder)
return -EINVAL;
