arm64: kvm: avoid overflow in integer division
The newly added kvm_mmu_split_nr_page_tables() function uses DIV_ROUND_DOWN_ULL()
to divide 64-bit addresses, but this requires a 32-bit divisior, and PUD_SIZE
may exceed that when 64KB pages are used:
arch/arm64/kvm/mmu.c: In function 'kvm_mmu_split_nr_page_tables':
include/linux/math.h:42:64: error: conversion from 'long unsigned int' to 'u32' {aka 'unsigned int'} changes value from '
68719476736' to '0' [-Werror=overflow]
42 | DIV_ROUND_DOWN_ULL((unsigned long long)(ll) + (d) - 1, (d))
| ^~~
include/linux/math.h:39:47: note: in definition of macro 'DIV_ROUND_DOWN_ULL'
39 | #define DIV_ROUND_DOWN_ULL(ll, d) div_u64(ll, d)
| ^
arch/arm64/kvm/mmu.c:95:22: note: in expansion of macro 'DIV_ROUND_UP_ULL'
95 | n += DIV_ROUND_UP_ULL(range, PUD_SIZE);
| ^~~~~~~~~~~~~~~~
Since this code is only used on 64-bit targets, DIV_ROUND_UP() can deal with this
more easily, as it already takes 64-bit arguments.
Fixes:
e7bf7a490c68 ("KVM: arm64: Split huge pages when dirty logging is enabled")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20230517202352.793673-1-arnd@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>