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Message-ID: <174611877481.22196.10244252918339863915.tip-bot2@tip-bot2>
Date: Thu, 01 May 2025 16:59:33 -0000
From: "tip-bot2 for Dan Williams" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Dan Williams <dan.j.williams@...el.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Nikolay Borisov <nik.borisov@...e.com>,
"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject:
[tip: x86/mm] x86/devmem: Remove duplicate range_is_allowed() definition
The following commit has been merged into the x86/mm branch of tip:
Commit-ID: 1b3f2bd04d90f61e1f291b5e365b9bc4ce0ea7c7
Gitweb: https://git.kernel.org/tip/1b3f2bd04d90f61e1f291b5e365b9bc4ce0ea7c7
Author: Dan Williams <dan.j.williams@...el.com>
AuthorDate: Tue, 29 Apr 2025 19:46:21 -07:00
Committer: Dave Hansen <dave.hansen@...ux.intel.com>
CommitterDate: Thu, 01 May 2025 09:43:48 -07:00
x86/devmem: Remove duplicate range_is_allowed() definition
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]
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Link: https://lore.kernel.org/all/20250430024622.1134277-2-dan.j.williams%40intel.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 72d8cbc..c97b659 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 169eed1..4883995 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 6a6bc4d..0642c7e 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 */
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