x86, mm: Create slow_virt_to_phys() (d7656534) · Commits · 戴 / test

This is necessary because __pa() does not work on some kinds of memory, like vmalloc() or the alloc_remap() areas on 32-bit NUMA systems. We have some functions to do conversions _like_ this in the vmalloc() code (like vmalloc_to_page()), but they do not work on sizes other than 4k pages. We would potentially need to be able to handle all the page sizes that we use for the kernel linear mapping (4k, 2M, 1G). In practice, on 32-bit NUMA systems, the percpu areas get stuck in the alloc_remap() area. Any __pa() call on them will break and basically return garbage. This patch introduces a new function slow_virt_to_phys(), which walks the kernel page tables on x86 and should do precisely the same logical thing as __pa(), but actually work on a wider range of memory. It should work on the normal linear mapping, vmalloc(), kmap(), etc... Signed-off-by:

Dave Hansen <dave@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/20130122212433.4D1FCA62@kernel.stglabs.ibm.com Acked-by:

Rik van Riel <riel@redhat.com> Signed-off-by:

H. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/pgtable_types.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -352,6 +352,7 @@ static inline void update_page_count(int level, unsigned long pages) { }
		* as a pte too.
		*/
		extern pte_t lookup_address(unsigned long address, unsigned int level);
		extern phys_addr_t slow_virt_to_phys(void *__address);

		#endif /* !__ASSEMBLY__ */

arch/x86/mm/pageattr.c

+31 −0

Original line number	Diff line number	Diff line
		@@ -363,6 +363,37 @@ pte_t lookup_address(unsigned long address, unsigned int level)
		}
		EXPORT_SYMBOL_GPL(lookup_address);

		/*
		* This is necessary because __pa() does not work on some
		* kinds of memory, like vmalloc() or the alloc_remap()
		* areas on 32-bit NUMA systems. The percpu areas can
		* end up in this kind of memory, for instance.
		*
		* This could be optimized, but it is only intended to be
		* used at inititalization time, and keeping it
		* unoptimized should increase the testing coverage for
		* the more obscure platforms.
		*/
		phys_addr_t slow_virt_to_phys(void *__virt_addr)
		{
		unsigned long virt_addr = (unsigned long)__virt_addr;
		phys_addr_t phys_addr;
		unsigned long offset;
		enum pg_level level;
		unsigned long psize;
		unsigned long pmask;
		pte_t *pte;

		pte = lookup_address(virt_addr, &level);
		BUG_ON(!pte);
		psize = page_level_size(level);
		pmask = page_level_mask(level);
		offset = virt_addr & ~pmask;
		phys_addr = pte_pfn(*pte) << PAGE_SHIFT;
		return (phys_addr \| offset);
		}
		EXPORT_SYMBOL_GPL(slow_virt_to_phys);

		/*
		* Set the new pmd in all the pgds we know about:
		*/

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