[PATCH AUTOSEL 6.1 21/42] RISC-V: Don't have MAX_PHYSMEM_BITS exceed phys_addr_t

Sasha Levin
2024-10-04T18:27:57Z

From: Palmer Dabbelt <palmer@rivosinc.com>

[ Upstream commit ad380f6a0a5e82e794b45bb2eaec24ed51a56846 ]

I recently ended up with a warning on some compilers along the lines of

CC kernel/resource.o
In file included from include/linux/ioport.h:16,
from kernel/resource.c:15:
kernel/resource.c: In function 'gfr_start':
include/linux/minmax.h:49:37: error: conversion from 'long long unsigned int' to 'resource_size_t' {aka 'unsigned int'} changes value from '17179869183' to '4294967295' [-Werror=overflow]
49 | ({ type ux = (x); type uy = (y); __cmp(op, ux, uy); })
| ^
include/linux/minmax.h:52:9: note: in expansion of macro '__cmp_once_unique'
52 | __cmp_once_unique(op, type, x, y, __UNIQUE_ID(x_), __UNIQUE_ID(y_))
| ^~~~~~~~~~~~~~~~~
include/linux/minmax.h:161:27: note: in expansion of macro '__cmp_once'
161 | #define min_t(type, x, y) __cmp_once(min, type, x, y)
| ^~~~~~~~~~
kernel/resource.c:1829:23: note: in expansion of macro 'min_t'
1829 | end = min_t(resource_size_t, base->end,
| ^~~~~
kernel/resource.c: In function 'gfr_continue':
include/linux/minmax.h:49:37: error: conversion from 'long long unsigned int' to 'resource_size_t' {aka 'unsigned int'} changes value from '17179869183' to '4294967295' [-Werror=overflow]
49 | ({ type ux = (x); type uy = (y); __cmp(op, ux, uy); })
| ^
include/linux/minmax.h:52:9: note: in expansion of macro '__cmp_once_unique'
52 | __cmp_once_unique(op, type, x, y, __UNIQUE_ID(x_), __UNIQUE_ID(y_))
| ^~~~~~~~~~~~~~~~~
include/linux/minmax.h:161:27: note: in expansion of macro '__cmp_once'
161 | #define min_t(type, x, y) __cmp_once(min, type, x, y)
| ^~~~~~~~~~
kernel/resource.c:1847:24: note: in expansion of macro 'min_t'
1847 | addr <= min_t(resource_size_t, base->end,
| ^~~~~
cc1: all warnings being treated as errors

which looks like a real problem: our phys_addr_t is only 32 bits now, so
having 34-bit masks is just going to result in overflows.

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240731162159.9235-2-palmer@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/riscv/include/asm/sparsemem.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/sparsemem.h b/arch/riscv/include/asm/sparsemem.h
index 63acaecc33747..2f901a410586d 100644
--- a/arch/riscv/include/asm/sparsemem.h
+++ b/arch/riscv/include/asm/sparsemem.h
@@ -7,7 +7,7 @@
#ifdef CONFIG_64BIT
#define MAX_PHYSMEM_BITS 56
#else
-#define MAX_PHYSMEM_BITS 34
+#define MAX_PHYSMEM_BITS 32
#endif /* CONFIG_64BIT */
#define SECTION_SIZE_BITS 27
#endif /* CONFIG_SPARSEMEM */
--
2.43.0