Attempt VMA lock-based page fault handling first, and fall back to the
existing mmap_lock-based handling if that fails.
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
---
arch/x86/Kconfig | 1 +
arch/x86/mm/fault.c | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3604074a878b..3647f7bdb110 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -27,6 +27,7 @@ config X86_64
# Options that are inherently 64-bit kernel only:
select ARCH_HAS_GIGANTIC_PAGE
select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
+ select ARCH_SUPPORTS_PER_VMA_LOCK
select ARCH_USE_CMPXCHG_LOCKREF
select HAVE_ARCH_SOFT_DIRTY
select MODULES_USE_ELF_RELA
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index a498ae1fbe66..122c8fe4af12 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -19,6 +19,7 @@
#include <linux/uaccess.h> /* faulthandler_disabled() */
#include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/
#include <linux/mm_types.h>
+#include <linux/mm.h> /* find_and_lock_vma() */
#include <asm/cpufeature.h> /* boot_cpu_has, ... */
#include <asm/traps.h> /* dotraplinkage, ... */
@@ -1333,6 +1334,38 @@ void do_user_addr_fault(struct pt_regs *regs,
}
#endif
+#ifdef CONFIG_PER_VMA_LOCK
+ if (!(flags & FAULT_FLAG_USER) || atomic_read(&mm->mm_users) == 1)
+ goto lock_mmap;
+
+ vma = lock_vma_under_rcu(mm, address);
+ if (!vma)
+ goto lock_mmap;
+
+ if (unlikely(access_error(error_code, vma))) {
+ vma_end_read(vma);
+ goto lock_mmap;
+ }
+ fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
+ vma_end_read(vma);
+
+ if (!(fault & VM_FAULT_RETRY)) {
+ count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+ goto done;
+ }
+ count_vm_vma_lock_event(VMA_LOCK_RETRY);
+
+ /* Quick path to respond to signals */
+ if (fault_signal_pending(fault, regs)) {
+ if (!user_mode(regs))
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ SIGBUS, BUS_ADRERR,
+ ARCH_DEFAULT_PKEY);
+ return;
+ }
+lock_mmap:
+#endif /* CONFIG_PER_VMA_LOCK */
+
/*
* Kernel-mode access to the user address space should only occur
* on well-defined single instructions listed in the exception
@@ -1433,6 +1466,9 @@ void do_user_addr_fault(struct pt_regs *regs,
}
mmap_read_unlock(mm);
+#ifdef CONFIG_PER_VMA_LOCK
+done:
+#endif
if (likely(!(fault & VM_FAULT_ERROR)))
return;
--
2.39.1
