The following commit has been merged into the x86/mm branch of tip:
Commit-ID: e0bddc19ba9578bc4e4c60a3f29ccc227277854c
Gitweb: https://git.kernel.org/tip/e0bddc19ba9578bc4e4c60a3f29ccc227277854c
Author: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
AuthorDate: Sun, 12 Mar 2023 14:26:02 +03:00
Committer: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Thu, 16 Mar 2023 13:08:39 -07:00
x86/mm: Reduce untagged_addr() overhead for systems without LAM
Use alternatives to reduce untagged_addr() overhead.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20230312112612.31869-8-kirill.shutemov%40linux.intel.com
---
arch/x86/include/asm/disabled-features.h | 8 +++-
arch/x86/include/asm/uaccess.h | 41 ++++++++++++++++-------
2 files changed, 37 insertions(+), 12 deletions(-)
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index 5dfa4fb..fafe9be 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -75,6 +75,12 @@
# define DISABLE_CALL_DEPTH_TRACKING (1 << (X86_FEATURE_CALL_DEPTH & 31))
#endif
+#ifdef CONFIG_ADDRESS_MASKING
+# define DISABLE_LAM 0
+#else
+# define DISABLE_LAM (1 << (X86_FEATURE_LAM & 31))
+#endif
+
#ifdef CONFIG_INTEL_IOMMU_SVM
# define DISABLE_ENQCMD 0
#else
@@ -115,7 +121,7 @@
#define DISABLED_MASK10 0
#define DISABLED_MASK11 (DISABLE_RETPOLINE|DISABLE_RETHUNK|DISABLE_UNRET| \
DISABLE_CALL_DEPTH_TRACKING)
-#define DISABLED_MASK12 0
+#define DISABLED_MASK12 (DISABLE_LAM)
#define DISABLED_MASK13 0
#define DISABLED_MASK14 0
#define DISABLED_MASK15 0
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index c79ebdb..457e814 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -9,6 +9,7 @@
#include <linux/kasan-checks.h>
#include <linux/mm_types.h>
#include <linux/string.h>
+#include <linux/mmap_lock.h>
#include <asm/asm.h>
#include <asm/page.h>
#include <asm/smap.h>
@@ -30,26 +31,44 @@ static inline bool pagefault_disabled(void);
* Magic with the 'sign' allows to untag userspace pointer without any branches
* while leaving kernel addresses intact.
*/
-static inline unsigned long __untagged_addr(unsigned long addr,
- unsigned long mask)
+static inline unsigned long __untagged_addr(unsigned long addr)
{
- long sign = addr >> 63;
+ long sign;
+
+ /*
+ * Refer tlbstate_untag_mask directly to avoid RIP-relative relocation
+ * in alternative instructions. The relocation gets wrong when gets
+ * copied to the target place.
+ */
+ asm (ALTERNATIVE("",
+ "sar $63, %[sign]\n\t" /* user_ptr ? 0 : -1UL */
+ "or %%gs:tlbstate_untag_mask, %[sign]\n\t"
+ "and %[sign], %[addr]\n\t", X86_FEATURE_LAM)
+ : [addr] "+r" (addr), [sign] "=r" (sign)
+ : "m" (tlbstate_untag_mask), "[sign]" (addr));
- addr &= mask | sign;
return addr;
}
#define untagged_addr(addr) ({ \
- u64 __addr = (__force u64)(addr); \
- __addr = __untagged_addr(__addr, current_untag_mask()); \
- (__force __typeof__(addr))__addr; \
+ unsigned long __addr = (__force unsigned long)(addr); \
+ (__force __typeof__(addr))__untagged_addr(__addr); \
})
+static inline unsigned long __untagged_addr_remote(struct mm_struct *mm,
+ unsigned long addr)
+{
+ long sign = addr >> 63;
+
+ mmap_assert_locked(mm);
+ addr &= (mm)->context.untag_mask | sign;
+
+ return addr;
+}
+
#define untagged_addr_remote(mm, addr) ({ \
- u64 __addr = (__force u64)(addr); \
- mmap_assert_locked(mm); \
- __addr = __untagged_addr(__addr, (mm)->context.untag_mask); \
- (__force __typeof__(addr))__addr; \
+ unsigned long __addr = (__force unsigned long)(addr); \
+ (__force __typeof__(addr))__untagged_addr_remote(mm, __addr); \
})
#else
|