[PATCH] x86/mm: Unify __phys_addr_symbol()

[PATCH] x86/mm: Unify __phys_addr_symbol()

[Brendan Jackman]

There are two implementations on 64-bit, depending on
CONFIG_DEBUG_VIRTUAL, but they differ only regarding the presence of
VIRTUAL_BUG_ON, which is already ifdef'd on CONFIG_DEBUG_VIRTUAL.

To avoid adding a function call on non-LTO non-DEBUG_VIRTUAL builds,
move the function into the header. (Note the function is already only
used on 64-bit).

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
Note: I started to unify __phys_addr() too since at first glance it also
seems to have the same unnecessary duplication. But actually for that
one there's code that needs to skip the VIRTUAL_BUG_ON() even when
CONFIG_DEBUG_VIRTUAL (via __pa_nodebug()).

I've run KUnit on x86_64 with DEBUG_VIRTUAL on and off.
---
 arch/x86/include/asm/page_64.h | 14 +++++++++++---
 arch/x86/mm/physaddr.c         | 11 -----------
 2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
index 015d23f3e01f12906d4a423ec555ea5fe53249c6..364c8d618fa7e9186f26ecff00d93d0b07882664 100644
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -9,6 +9,7 @@
 #include <asm/alternative.h>
 
 #include <linux/kmsan-checks.h>
+#include <linux/mmdebug.h>
 
 /* duplicated to the one in bootmem.h */
 extern unsigned long max_pfn;
@@ -31,13 +32,20 @@ static __always_inline unsigned long __phys_addr_nodebug(unsigned long x)
 
 #ifdef CONFIG_DEBUG_VIRTUAL
 extern unsigned long __phys_addr(unsigned long);
-extern unsigned long __phys_addr_symbol(unsigned long);
 #else
 #define __phys_addr(x)		__phys_addr_nodebug(x)
-#define __phys_addr_symbol(x) \
-	((unsigned long)(x) - __START_KERNEL_map + phys_base)
 #endif
 
+static inline unsigned long __phys_addr_symbol(unsigned long x)
+{
+	unsigned long y = x - __START_KERNEL_map;
+
+	/* only check upper bounds since lower bounds will trigger carry */
+	VIRTUAL_BUG_ON(y >= KERNEL_IMAGE_SIZE);
+
+	return y + phys_base;
+}
+
 #define __phys_reloc_hide(x)	(x)
 
 void clear_page_orig(void *page);
diff --git a/arch/x86/mm/physaddr.c b/arch/x86/mm/physaddr.c
index fc3f3d3e2ef210fc31b2eb661f4c5f73457d42ab..8d31c6b9e184ff2110ef896e63eb6422070d8b1d 100644
--- a/arch/x86/mm/physaddr.c
+++ b/arch/x86/mm/physaddr.c
@@ -31,17 +31,6 @@ unsigned long __phys_addr(unsigned long x)
 	return x;
 }
 EXPORT_SYMBOL(__phys_addr);
-
-unsigned long __phys_addr_symbol(unsigned long x)
-{
-	unsigned long y = x - __START_KERNEL_map;
-
-	/* only check upper bounds since lower bounds will trigger carry */
-	VIRTUAL_BUG_ON(y >= KERNEL_IMAGE_SIZE);
-
-	return y + phys_base;
-}
-EXPORT_SYMBOL(__phys_addr_symbol);
 #endif
 
 bool __virt_addr_valid(unsigned long x)

---
base-commit: 8742b2d8935f476449ef37e263bc4da3295c7b58
change-id: 20250813-phys-addr-cleanup-d85f181534e7

Best regards,
-- 
Brendan Jackman <jackmanb@google.com>

Re: [PATCH] x86/mm: Unify __phys_addr_symbol()

[Dave Hansen]

On 8/13/25 08:08, Brendan Jackman wrote:
> There are two implementations on 64-bit, depending on
> CONFIG_DEBUG_VIRTUAL, but they differ only regarding the presence of
> VIRTUAL_BUG_ON, which is already ifdef'd on CONFIG_DEBUG_VIRTUAL.
> 
> To avoid adding a function call on non-LTO non-DEBUG_VIRTUAL builds,
> move the function into the header. (Note the function is already only
> used on 64-bit).

... and just for the record CONFIG_DEBUG_VIRTUAL really is a
debug-build-only thing. I don't see it set in any normal distro kernels.
This shouldn't bloat any normal builds, although it will probably make
CONFIG_DEBUG_VIRTUAL=y build bigger. But I don't think we care about that.

Acked-by: Dave Hansen <dave.hansen@linux.intel.com>