cxl/region´╝ÜFix overflow issue in alloc_hpa()

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 <>
Reviewed-by: Dave Jiang <>
Fixes: 23a22cd1c98b ("cxl/region: Allocate HPA capacity to regions")
Cc: <>
Signed-off-by: Dan Williams <>
1 file changed