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

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Message-ID: <20241004182718.3673735-21-sashal@kernel.org>
Date: Fri,  4 Oct 2024 14:26:32 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Palmer Dabbelt <palmer@...osinc.com>,
	Charlie Jenkins <charlie@...osinc.com>,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Sasha Levin <sashal@...nel.org>,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	linux-riscv@...ts.infradead.org
Subject: [PATCH AUTOSEL 6.1 21/42] RISC-V: Don't have MAX_PHYSMEM_BITS exceed phys_addr_t

From: Palmer Dabbelt <palmer@...osinc.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@...osinc.com>
Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>
Link: https://lore.kernel.org/r/20240731162159.9235-2-palmer@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
Signed-off-by: Sasha Levin <sashal@...nel.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