page_to_phys is duplicated by all architectures, and from some strange
reason placed in <asm/io.h> where it doesn't fit at all.

phys_to_page is only provided by a few architectures despite having a lot
of open coded users.

Provide generic versions in <asm-generic/memory_model.h> to make these
helpers more easily usable.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/alpha/include/asm/io.h         |  1 -
 arch/arc/include/asm/io.h           |  3 ---
 arch/arm/include/asm/memory.h       |  6 ------
 arch/arm64/include/asm/memory.h     |  6 ------
 arch/csky/include/asm/page.h        |  3 ---
 arch/hexagon/include/asm/page.h     |  6 ------
 arch/loongarch/include/asm/page.h   |  3 ---
 arch/m68k/include/asm/virtconvert.h |  3 ---
 arch/microblaze/include/asm/page.h  |  1 -
 arch/mips/include/asm/io.h          |  5 -----
 arch/nios2/include/asm/io.h         |  3 ---
 arch/openrisc/include/asm/page.h    |  2 --
 arch/parisc/include/asm/page.h      |  1 -
 arch/powerpc/include/asm/io.h       | 12 ------------
 arch/riscv/include/asm/page.h       |  3 ---
 arch/s390/include/asm/page.h        |  2 --
 arch/sh/include/asm/page.h          |  1 -
 arch/sparc/include/asm/page.h       |  2 --
 arch/um/include/asm/pgtable.h       |  2 --
 arch/x86/include/asm/io.h           |  5 -----
 arch/xtensa/include/asm/page.h      |  1 -
 include/asm-generic/memory_model.h  |  3 +++
 22 files changed, 3 insertions(+), 71 deletions(-)

diff --git a/arch/alpha/include/asm/io.h b/arch/alpha/include/asm/io.h
index b191d87f89c401..65fe1e54c6da09 100644
--- a/arch/alpha/include/asm/io.h
+++ b/arch/alpha/include/asm/io.h
@@ -88,7 +88,6 @@ static inline void * phys_to_virt(unsigned long address)
 
 #define virt_to_phys		virt_to_phys
 #define phys_to_virt		phys_to_virt
-#define page_to_phys(page)	page_to_pa(page)
 
 /* Maximum PIO space address supported?  */
 #define IO_SPACE_LIMIT 0xffff
diff --git a/arch/arc/include/asm/io.h b/arch/arc/include/asm/io.h
index f57cb5a6b62403..00171a212b3cb2 100644
--- a/arch/arc/include/asm/io.h
+++ b/arch/arc/include/asm/io.h
@@ -42,9 +42,6 @@ static inline void ioport_unmap(void __iomem *addr)
 #define iowrite16be(v,p)	({ __iowmb(); __raw_writew((__force u16)cpu_to_be16(v), p); })
 #define iowrite32be(v,p)	({ __iowmb(); __raw_writel((__force u32)cpu_to_be32(v), p); })
 
-/* Change struct page to physical address */
-#define page_to_phys(page)		(page_to_pfn(page) << PAGE_SHIFT)
-
 #define __raw_readb __raw_readb
 static inline u8 __raw_readb(const volatile void __iomem *addr)
 {
diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index ef2aa79ece5ad5..7c2fa7dcec6d4b 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -147,12 +147,6 @@ extern unsigned long vectors_base;
 #define DTCM_OFFSET	UL(0xfffe8000)
 #endif
 
-/*
- * Convert a page to/from a physical address
- */
-#define page_to_phys(page)	(__pfn_to_phys(page_to_pfn(page)))
-#define phys_to_page(phys)	(pfn_to_page(__phys_to_pfn(phys)))
-
 /*
  * PLAT_PHYS_OFFSET is the offset (from zero) of the start of physical
  * memory.  This is used for XIP and NoMMU kernels, and on platforms that don't
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 0480c61dbb4f30..b9b992908a569c 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -353,12 +353,6 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x);
 #define __phys_to_virt(x)	((unsigned long)((x) - PHYS_OFFSET) | PAGE_OFFSET)
 #define __phys_to_kimg(x)	((unsigned long)((x) + kimage_voffset))
 
-/*
- * Convert a page to/from a physical address
- */
-#define page_to_phys(page)	(__pfn_to_phys(page_to_pfn(page)))
-#define phys_to_page(phys)	(pfn_to_page(__phys_to_pfn(phys)))
-
 /*
  * Note: Drivers should NOT use these.  They are the wrong
  * translation for translating DMA addresses.  Use the driver
diff --git a/arch/csky/include/asm/page.h b/arch/csky/include/asm/page.h
index 0ca6c408c07f27..a5afdfe27dc62d 100644
--- a/arch/csky/include/asm/page.h
+++ b/arch/csky/include/asm/page.h
@@ -43,9 +43,6 @@ extern void *memcpy(void *to, const void *from, size_t l);
 #define clear_page(page)	memset((page), 0, PAGE_SIZE)
 #define copy_page(to, from)	memcpy((to), (from), PAGE_SIZE)
 
-#define page_to_phys(page)	(page_to_pfn(page) << PAGE_SHIFT)
-#define phys_to_page(paddr)	(pfn_to_page(PFN_DOWN(paddr)))
-
 struct page;
 
 #include <abi/page.h>
diff --git a/arch/hexagon/include/asm/page.h b/arch/hexagon/include/asm/page.h
index 8a6af57274c2db..aba4d790130518 100644
--- a/arch/hexagon/include/asm/page.h
+++ b/arch/hexagon/include/asm/page.h
@@ -118,12 +118,6 @@ static inline void clear_page(void *page)
 #define clear_user_page(page, vaddr, pg)	clear_page(page)
 #define copy_user_page(to, from, vaddr, pg)	copy_page(to, from)
 
-/*
- * page_to_phys - convert page to physical address
- * @page - pointer to page entry in mem_map
- */
-#define page_to_phys(page)      (page_to_pfn(page) << PAGE_SHIFT)
-
 static inline unsigned long virt_to_pfn(const void *kaddr)
 {
 	return __pa(kaddr) >> PAGE_SHIFT;
diff --git a/arch/loongarch/include/asm/page.h b/arch/loongarch/include/asm/page.h
index e85df33f11c772..8b4e6b280f2b86 100644
--- a/arch/loongarch/include/asm/page.h
+++ b/arch/loongarch/include/asm/page.h
@@ -81,9 +81,6 @@ struct page *tlb_virt_to_page(unsigned long kaddr);
 #define pfn_to_phys(pfn)	__pfn_to_phys(pfn)
 #define phys_to_pfn(paddr)	__phys_to_pfn(paddr)
 
-#define page_to_phys(page)	pfn_to_phys(page_to_pfn(page))
-#define phys_to_page(paddr)	pfn_to_page(phys_to_pfn(paddr))
-
 #ifndef CONFIG_KFENCE
 
 #define page_to_virt(page)	__va(page_to_phys(page))
diff --git a/arch/m68k/include/asm/virtconvert.h b/arch/m68k/include/asm/virtconvert.h
index 0a27905b0036ff..32e27bddb7d430 100644
--- a/arch/m68k/include/asm/virtconvert.h
+++ b/arch/m68k/include/asm/virtconvert.h
@@ -28,9 +28,6 @@ static inline void *phys_to_virt(unsigned long address)
 	return __va(address);
 }
 
-/* Permanent address of a page. */
-#define page_to_phys(page)	(page_to_pfn(page) << PAGE_SHIFT)
-
 /*
  * IO bus memory addresses are 1:1 with the physical address,
  * deprecated globally but still used on two machines.
diff --git a/arch/microblaze/include/asm/page.h b/arch/microblaze/include/asm/page.h
index 8810f4f1c3b02d..ecd4bf2779a0bb 100644
--- a/arch/microblaze/include/asm/page.h
+++ b/arch/microblaze/include/asm/page.h
@@ -101,7 +101,6 @@ extern int page_is_ram(unsigned long pfn);
 
 #  define virt_to_page(kaddr)	(pfn_to_page(__pa(kaddr) >> PAGE_SHIFT))
 #  define page_to_virt(page)   __va(page_to_pfn(page) << PAGE_SHIFT)
-#  define page_to_phys(page)     (page_to_pfn(page) << PAGE_SHIFT)
 
 #  define ARCH_PFN_OFFSET	(memory_start >> PAGE_SHIFT)
 # endif /* __ASSEMBLY__ */
diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h
index af58d6ae06b85e..0bddb568af7c1c 100644
--- a/arch/mips/include/asm/io.h
+++ b/arch/mips/include/asm/io.h
@@ -125,11 +125,6 @@ static inline unsigned long isa_virt_to_bus(volatile void *address)
 	return virt_to_phys(address);
 }
 
-/*
- * Change "struct page" to physical address.
- */
-#define page_to_phys(page)	((dma_addr_t)page_to_pfn(page) << PAGE_SHIFT)
-
 void __iomem *ioremap_prot(phys_addr_t offset, unsigned long size,
 		unsigned long prot_val);
 void iounmap(const volatile void __iomem *addr);
diff --git a/arch/nios2/include/asm/io.h b/arch/nios2/include/asm/io.h
index 746853ac7d8d38..36e3550673b34b 100644
--- a/arch/nios2/include/asm/io.h
+++ b/arch/nios2/include/asm/io.h
@@ -28,9 +28,6 @@
 void __iomem *ioremap(unsigned long physaddr, unsigned long size);
 void iounmap(void __iomem *addr);
 
-/* Pages to physical address... */
-#define page_to_phys(page)	virt_to_phys(page_to_virt(page))
-
 /* Macros used for converting between virtual and physical mappings. */
 #define phys_to_virt(vaddr)	\
 	((void *)((unsigned long)(vaddr) | CONFIG_NIOS2_KERNEL_REGION_BASE))
diff --git a/arch/openrisc/include/asm/page.h b/arch/openrisc/include/asm/page.h
index 1d5913f67c312f..45d6c440729ce3 100644
--- a/arch/openrisc/include/asm/page.h
+++ b/arch/openrisc/include/asm/page.h
@@ -80,8 +80,6 @@ static inline unsigned long virt_to_pfn(const void *kaddr)
 #define virt_to_page(addr) \
 	(mem_map + (((unsigned long)(addr)-PAGE_OFFSET) >> PAGE_SHIFT))
 
-#define page_to_phys(page)      ((dma_addr_t)page_to_pfn(page) << PAGE_SHIFT)
-
 #define virt_addr_valid(kaddr)	(pfn_valid(virt_to_pfn(kaddr)))
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/parisc/include/asm/page.h b/arch/parisc/include/asm/page.h
index 4bea2e95798f02..6cb5b02aca9a77 100644
--- a/arch/parisc/include/asm/page.h
+++ b/arch/parisc/include/asm/page.h
@@ -168,7 +168,6 @@ extern int npmem_ranges;
 
 #define virt_addr_valid(kaddr)	pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
 
-#define page_to_phys(page)	(page_to_pfn(page) << PAGE_SHIFT)
 #define virt_to_page(kaddr)     pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
 
 #include <asm-generic/memory_model.h>
diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h
index 52e1b1d15ff63a..fd92ac4501693c 100644
--- a/arch/powerpc/include/asm/io.h
+++ b/arch/powerpc/include/asm/io.h
@@ -969,18 +969,6 @@ static inline void * phys_to_virt(unsigned long address)
 }
 #define phys_to_virt phys_to_virt
 
-/*
- * Change "struct page" to physical address.
- */
-static inline phys_addr_t page_to_phys(struct page *page)
-{
-	unsigned long pfn = page_to_pfn(page);
-
-	WARN_ON(IS_ENABLED(CONFIG_DEBUG_VIRTUAL) && !pfn_valid(pfn));
-
-	return PFN_PHYS(pfn);
-}
-
 /*
  * 32 bits still uses virt_to_bus() for its implementation of DMA
  * mappings se we have to keep it defined here. We also have some old
diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index 32d308a3355fd4..16f4141f005561 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -194,9 +194,6 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x);
 #define virt_to_page(vaddr)	(pfn_to_page(virt_to_pfn(vaddr)))
 #define page_to_virt(page)	(pfn_to_virt(page_to_pfn(page)))
 
-#define page_to_phys(page)	(pfn_to_phys(page_to_pfn(page)))
-#define phys_to_page(paddr)	(pfn_to_page(phys_to_pfn(paddr)))
-
 #define sym_to_pfn(x)           __phys_to_pfn(__pa_symbol(x))
 
 unsigned long kaslr_offset(void);
diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 73e1e03317b433..16d62a4eccccef 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -245,9 +245,7 @@ static inline unsigned long __phys_addr(unsigned long x, bool is_31bit)
 #define phys_to_pfn(phys)	((phys) >> PAGE_SHIFT)
 #define pfn_to_phys(pfn)	((pfn) << PAGE_SHIFT)
 
-#define phys_to_page(phys)	pfn_to_page(phys_to_pfn(phys))
 #define phys_to_folio(phys)	page_folio(phys_to_page(phys))
-#define page_to_phys(page)	pfn_to_phys(page_to_pfn(page))
 #define folio_to_phys(page)	pfn_to_phys(folio_pfn(folio))
 
 static inline void *pfn_to_virt(unsigned long pfn)
diff --git a/arch/sh/include/asm/page.h b/arch/sh/include/asm/page.h
index f780b467e75d7c..4e82ea84a06fce 100644
--- a/arch/sh/include/asm/page.h
+++ b/arch/sh/include/asm/page.h
@@ -147,7 +147,6 @@ typedef struct page *pgtable_t;
 #endif
 
 #define pfn_to_kaddr(pfn)	__va((pfn) << PAGE_SHIFT)
-#define page_to_phys(page)	(page_to_pfn(page) << PAGE_SHIFT)
 
 /*
  * PFN = physical frame number (ie PFN 0 == physical address 0)
diff --git a/arch/sparc/include/asm/page.h b/arch/sparc/include/asm/page.h
index 5e44cdf2a8f2bd..1a00cc0a1893eb 100644
--- a/arch/sparc/include/asm/page.h
+++ b/arch/sparc/include/asm/page.h
@@ -2,8 +2,6 @@
 #ifndef ___ASM_SPARC_PAGE_H
 #define ___ASM_SPARC_PAGE_H
 
-#define page_to_phys(page)	(page_to_pfn(page) << PAGE_SHIFT)
-
 #if defined(__sparc__) && defined(__arch64__)
 #include <asm/page_64.h>
 #else
diff --git a/arch/um/include/asm/pgtable.h b/arch/um/include/asm/pgtable.h
index 83373c9963e7c9..faab5a2a4b061f 100644
--- a/arch/um/include/asm/pgtable.h
+++ b/arch/um/include/asm/pgtable.h
@@ -287,9 +287,7 @@ static inline int pte_same(pte_t pte_a, pte_t pte_b)
  * and a page entry and page directory to the page they refer to.
  */
 
-#define phys_to_page(phys) pfn_to_page(phys_to_pfn(phys))
 #define __virt_to_page(virt) phys_to_page(__pa(virt))
-#define page_to_phys(page) pfn_to_phys(page_to_pfn(page))
 #define virt_to_page(addr) __virt_to_page((const unsigned long) addr)
 
 #define mk_pte(page, pgprot) \
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 1d60427379c939..ed580c7f9d0aaf 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -151,11 +151,6 @@ static inline void *phys_to_virt(phys_addr_t address)
 }
 #define phys_to_virt phys_to_virt
 
-/*
- * Change "struct page" to physical address.
- */
-#define page_to_phys(page)    ((dma_addr_t)page_to_pfn(page) << PAGE_SHIFT)
-
 /*
  * ISA I/O bus memory addresses are 1:1 with the physical address.
  * However, we truncate the address to unsigned int to avoid undesirable
diff --git a/arch/xtensa/include/asm/page.h b/arch/xtensa/include/asm/page.h
index 4db56ef052d223..dc3d5b094ecd98 100644
--- a/arch/xtensa/include/asm/page.h
+++ b/arch/xtensa/include/asm/page.h
@@ -195,7 +195,6 @@ static inline unsigned long ___pa(unsigned long va)
 #define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
 #define page_to_virt(page)	__va(page_to_pfn(page) << PAGE_SHIFT)
 #define virt_addr_valid(kaddr)	pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
-#define page_to_phys(page)	(page_to_pfn(page) << PAGE_SHIFT)
 
 #endif /* __ASSEMBLY__ */
 
diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
index 6796abe1900e30..3d51066f88f819 100644
--- a/include/asm-generic/memory_model.h
+++ b/include/asm-generic/memory_model.h
@@ -64,6 +64,9 @@ static inline int pfn_valid(unsigned long pfn)
 #define page_to_pfn __page_to_pfn
 #define pfn_to_page __pfn_to_page
 
+#define page_to_phys(page)	__pfn_to_phys(page_to_pfn(page))
+#define phys_to_page(phys)	pfn_to_page(__phys_to_pfn(phys))
+
 #endif /* __ASSEMBLY__ */
 
 #endif
-- 
2.45.2

Le 09/10/2024 à 13:43, Christoph Hellwig a écrit :
> page_to_phys is duplicated by all architectures, and from some strange
> reason placed in <asm/io.h> where it doesn't fit at all.
> 
> phys_to_page is only provided by a few architectures despite having a lot
> of open coded users.
> 
> Provide generic versions in <asm-generic/memory_model.h> to make these
> helpers more easily usable.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   arch/alpha/include/asm/io.h         |  1 -
>   arch/arc/include/asm/io.h           |  3 ---
>   arch/arm/include/asm/memory.h       |  6 ------
>   arch/arm64/include/asm/memory.h     |  6 ------
>   arch/csky/include/asm/page.h        |  3 ---
>   arch/hexagon/include/asm/page.h     |  6 ------
>   arch/loongarch/include/asm/page.h   |  3 ---
>   arch/m68k/include/asm/virtconvert.h |  3 ---
>   arch/microblaze/include/asm/page.h  |  1 -
>   arch/mips/include/asm/io.h          |  5 -----
>   arch/nios2/include/asm/io.h         |  3 ---
>   arch/openrisc/include/asm/page.h    |  2 --
>   arch/parisc/include/asm/page.h      |  1 -
>   arch/powerpc/include/asm/io.h       | 12 ------------

As far as I understand, this patch silently drops part of commit 
6bf752daca07 ("powerpc: implement CONFIG_DEBUG_VIRTUAL").

Can you please clarify ?

Christophe

On Wed, Oct 9, 2024, at 11:43, Christoph Hellwig wrote:
> page_to_phys is duplicated by all architectures, and from some strange
> reason placed in <asm/io.h> where it doesn't fit at all.
>
> phys_to_page is only provided by a few architectures despite having a lot
> of open coded users.
>
> Provide generic versions in <asm-generic/memory_model.h> to make these
> helpers more easily usable.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

This is clearly a good idea, and I'm happy to take that through
the asm-generic tree if there are no complaints.

Do you have any other patches that depend on it?

> -/*
> - * Change "struct page" to physical address.
> - */
> -static inline phys_addr_t page_to_phys(struct page *page)
> -{
> -	unsigned long pfn = page_to_pfn(page);
> -
> -	WARN_ON(IS_ENABLED(CONFIG_DEBUG_VIRTUAL) && !pfn_valid(pfn));
> -
> -	return PFN_PHYS(pfn);
> -}

This part is technically a change in behavior, not sure how
much anyone cares.

> diff --git a/include/asm-generic/memory_model.h 
> b/include/asm-generic/memory_model.h
> index 6796abe1900e30..3d51066f88f819 100644
> --- a/include/asm-generic/memory_model.h
> +++ b/include/asm-generic/memory_model.h
> @@ -64,6 +64,9 @@ static inline int pfn_valid(unsigned long pfn)
>  #define page_to_pfn __page_to_pfn
>  #define pfn_to_page __pfn_to_page
> 
> +#define page_to_phys(page)	__pfn_to_phys(page_to_pfn(page))
> +#define phys_to_page(phys)	pfn_to_page(__phys_to_pfn(phys))

I think we should try to have a little fewer nested macros
to evaluate here, right now this ends up expanding
__pfn_to_phys, PFN_PHYS, PAGE_SHIFT, CONFIG_PAGE_SHIFT,
page_to_pfn and __page_to_pfn. While the behavior is fine,
modern gcc versions list all of those in an warning message
if someone passes the wrong arguments.

Changing the two macros above into inline functions
would help as well, but may cause other problems.

On a related note, it would be even better if we could come
up with a generic definition for either __pa/__va or
virt_to_phys/phys_to_virt. Most architectures define one
of the two pairs in terms of the other, which leads to
confusion with header include order.

      Arnd

On Wed, Oct 09, 2024 at 02:06:27PM +0000, Arnd Bergmann wrote:
> This is clearly a good idea, and I'm happy to take that through
> the asm-generic tree if there are no complaints.
> 
> Do you have any other patches that depend on it?

Well, I have new code that would benefit from these helpers, but just
open coding it for now and then doing a swipe to clean that up later
together with the existing open coded versions is easy enough.

> > -/*
> > - * Change "struct page" to physical address.
> > - */
> > -static inline phys_addr_t page_to_phys(struct page *page)
> > -{
> > -	unsigned long pfn = page_to_pfn(page);
> > -
> > -	WARN_ON(IS_ENABLED(CONFIG_DEBUG_VIRTUAL) && !pfn_valid(pfn));
> > -
> > -	return PFN_PHYS(pfn);
> > -}
> 
> This part is technically a change in behavior, not sure how
> much anyone cares.

Well, the only other comment to the patch so far mentioned it.
It also feels like a useful check, but I'm a bit worried about
it triggering in various new places.  Although that's just with
CONFIG_DEBUG_VIRTUAL and probably points to real bugs, so maybe
adding it everywhere is a good idea.

> > +#define page_to_phys(page)	__pfn_to_phys(page_to_pfn(page))
> > +#define phys_to_page(phys)	pfn_to_page(__phys_to_pfn(phys))
> 
> I think we should try to have a little fewer nested macros
> to evaluate here, right now this ends up expanding
> __pfn_to_phys, PFN_PHYS, PAGE_SHIFT, CONFIG_PAGE_SHIFT,
> page_to_pfn and __page_to_pfn. While the behavior is fine,
> modern gcc versions list all of those in an warning message
> if someone passes the wrong arguments.
> 
> Changing the two macros above into inline functions
> would help as well, but may cause other problems.

Doing them as inlines seems useful to me, let me throw that at
the buildbot and see if anything explodes.

> On a related note, it would be even better if we could come
> up with a generic definition for either __pa/__va or
> virt_to_phys/phys_to_virt. Most architectures define one
> of the two pairs in terms of the other, which leads to
> confusion with header include order.

Agreed, but that's a separate project.

On Thu, Oct 10, 2024 at 09:03:42AM +0200, Christoph Hellwig wrote:
> > I think we should try to have a little fewer nested macros
> > to evaluate here, right now this ends up expanding
> > __pfn_to_phys, PFN_PHYS, PAGE_SHIFT, CONFIG_PAGE_SHIFT,
> > page_to_pfn and __page_to_pfn. While the behavior is fine,
> > modern gcc versions list all of those in an warning message
> > if someone passes the wrong arguments.
> > 
> > Changing the two macros above into inline functions
> > would help as well, but may cause other problems.
> 
> Doing them as inlines seems useful to me, let me throw that at
> the buildbot and see if anything explodes.

The inline version instantly blows up, so I'll try just open coding
the phys to/from pfn translation instead.