17 years ago, Venki suggested [1] "A future improvement would be to avoid the range_is_allowed duplication".
The only thing preventing a common implementation is that phys_mem_access_prot_allowed() expects the range check to exit immediately when PAT is disabled [2]. I.e. there is no cache conflict to manage in that case. This cleanup was noticed on the path to considering changing range_is_allowed() policy to blanket deny /dev/mem for private (confidential computing) memory.
Note, however that phys_mem_access_prot_allowed() has long since stopped being relevant for managing cache-type validation due to [3], and [4].
Commit 0124cecfc85a ("x86, PAT: disable /dev/mem mmap RAM with PAT") [1] Commit 9e41bff2708e ("x86: fix /dev/mem mmap breakage when PAT is disabled") [2] Commit 1886297ce0c8 ("x86/mm/pat: Fix BUG_ON() in mmap_mem() on QEMU/i386") [3] Commit 0c3c8a18361a ("x86, PAT: Remove duplicate memtype reserve in devmem mmap") [4]
Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Ingo Molnar mingo@kernel.org Cc: "Naveen N Rao" naveen@kernel.org Reviewed-by: Nikolay Borisov nik.borisov@suse.com Signed-off-by: Dan Williams dan.j.williams@intel.com --- arch/x86/mm/pat/memtype.c | 31 ++++--------------------------- drivers/char/mem.c | 18 ------------------ include/linux/io.h | 21 +++++++++++++++++++++ 3 files changed, 25 insertions(+), 45 deletions(-)
diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c index 72d8cbc61158..c97b6598f187 100644 --- a/arch/x86/mm/pat/memtype.c +++ b/arch/x86/mm/pat/memtype.c @@ -38,6 +38,7 @@ #include <linux/kernel.h> #include <linux/pfn_t.h> #include <linux/slab.h> +#include <linux/io.h> #include <linux/mm.h> #include <linux/highmem.h> #include <linux/fs.h> @@ -773,38 +774,14 @@ pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn, return vma_prot; }
-#ifdef CONFIG_STRICT_DEVMEM -/* This check is done in drivers/char/mem.c in case of STRICT_DEVMEM */ -static inline int range_is_allowed(unsigned long pfn, unsigned long size) -{ - return 1; -} -#else -/* This check is needed to avoid cache aliasing when PAT is enabled */ -static inline int range_is_allowed(unsigned long pfn, unsigned long size) -{ - u64 from = ((u64)pfn) << PAGE_SHIFT; - u64 to = from + size; - u64 cursor = from; - - if (!pat_enabled()) - return 1; - - while (cursor < to) { - if (!devmem_is_allowed(pfn)) - return 0; - cursor += PAGE_SIZE; - pfn++; - } - return 1; -} -#endif /* CONFIG_STRICT_DEVMEM */ - int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn, unsigned long size, pgprot_t *vma_prot) { enum page_cache_mode pcm = _PAGE_CACHE_MODE_WB;
+ if (!pat_enabled()) + return 1; + if (!range_is_allowed(pfn, size)) return 0;
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 169eed162a7f..48839958b0b1 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -61,29 +61,11 @@ static inline int page_is_allowed(unsigned long pfn) { return devmem_is_allowed(pfn); } -static inline int range_is_allowed(unsigned long pfn, unsigned long size) -{ - u64 from = ((u64)pfn) << PAGE_SHIFT; - u64 to = from + size; - u64 cursor = from; - - while (cursor < to) { - if (!devmem_is_allowed(pfn)) - return 0; - cursor += PAGE_SIZE; - pfn++; - } - return 1; -} #else static inline int page_is_allowed(unsigned long pfn) { return 1; } -static inline int range_is_allowed(unsigned long pfn, unsigned long size) -{ - return 1; -} #endif
static inline bool should_stop_iteration(void) diff --git a/include/linux/io.h b/include/linux/io.h index 6a6bc4d46d0a..0642c7ee41db 100644 --- a/include/linux/io.h +++ b/include/linux/io.h @@ -183,4 +183,25 @@ static inline void arch_io_free_memtype_wc(resource_size_t base, int devm_arch_io_reserve_memtype_wc(struct device *dev, resource_size_t start, resource_size_t size);
+#ifdef CONFIG_STRICT_DEVMEM +static inline int range_is_allowed(unsigned long pfn, unsigned long size) +{ + u64 from = ((u64)pfn) << PAGE_SHIFT; + u64 to = from + size; + u64 cursor = from; + + while (cursor < to) { + if (!devmem_is_allowed(pfn)) + return 0; + cursor += PAGE_SIZE; + pfn++; + } + return 1; +} +#else +static inline int range_is_allowed(unsigned long pfn, unsigned long size) +{ + return 1; +} +#endif #endif /* _LINUX_IO_H */