[PATCH] arm64: kvm: fix gcc-10 shift warning

Arnd Bergmann
2020-04-29T18:58:30Z

gcc-10 warns that the 32-bit zero cannot be shifted more than
32 bits to the right:

arch/arm64/kvm/../../../virt/kvm/arm/mmu.c: In function 'clear_hyp_p4d_entry':
arch/arm64/include/asm/pgtable.h:630:35: error: right shift count >= width of type [-Werror=shift-count-overflow]
630 | #define pud_index(addr) (((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
| ^~
arch/arm64/include/asm/memory.h:271:45: note: in definition of macro '__phys_to_virt'
271 | #define __phys_to_virt(x) ((unsigned long)((x) - physvirt_offset))
| ^
arch/arm64/include/asm/pgtable.h:633:42: note: in expansion of macro '__va'
633 | #define pud_offset(dir, addr) ((pud_t *)__va(pud_offset_phys((dir), (addr))))
| ^~~~
arch/arm64/include/asm/pgtable.h:632:73: note: in expansion of macro 'pud_index'
632 | #define pud_offset_phys(dir, addr) (p4d_page_paddr(READ_ONCE(*(dir))) + pud_index(addr) * sizeof(pud_t))
| ^~~~~~~~~
arch/arm64/include/asm/pgtable.h:633:47: note: in expansion of macro 'pud_offset_phys'
633 | #define pud_offset(dir, addr) ((pud_t *)__va(pud_offset_phys((dir), (addr))))
| ^~~~~~~~~~~~~~~
arch/arm64/kvm/../../../virt/kvm/arm/mmu.c:510:36: note: in expansion of macro 'pud_offset'
510 | pud_t *pud_table __maybe_unused = pud_offset(p4d, 0);
| ^~~~~~~~~~

This is harmless, and the warning is a little bit silly for
a zero constant, but it's trivial to fix by making it an
unsigned long, so do that.

Fixes: 22998131ab33 ("arm64: add support for folded p4d page tables")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
virt/kvm/arm/mmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 48d4288c5f1b..534d9798c3cb 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -507,7 +507,7 @@ static void clear_hyp_pgd_entry(pgd_t *pgd)

static void clear_hyp_p4d_entry(p4d_t *p4d)
{
- pud_t *pud_table __maybe_unused = pud_offset(p4d, 0);
+ pud_t *pud_table __maybe_unused = pud_offset(p4d, 0UL);
VM_BUG_ON(p4d_huge(*p4d));
p4d_clear(p4d);
pud_free(NULL, pud_table);
--
2.26.0