The patch titled
Subject: x86/mm: try VMA lock-based page fault handling first
has been added to the -mm mm-unstable branch. Its filename is
x86-mm-try-vma-lock-based-page-fault-handling-first.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/x86-mm-try-vma-lock-based-page-fault-handling-first.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Subject: x86/mm: try VMA lock-based page fault handling first
Date: Mon, 27 Feb 2023 09:36:28 -0800
Attempt VMA lock-based page fault handling first, and fall back to the
existing mmap_lock-based handling if that fails.
Link: https://lkml.kernel.org/r/20230227173632.3292573-30-surenb@xxxxxxxxxx
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/arch/x86/Kconfig~x86-mm-try-vma-lock-based-page-fault-handling-first
+++ a/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
--- a/arch/x86/mm/fault.c~x86-mm-try-vma-lock-based-page-fault-handling-first
+++ a/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 *
}
#endif
+#ifdef CONFIG_PER_VMA_LOCK
+ if (!(flags & FAULT_FLAG_USER))
+ 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 @@ good_area:
}
mmap_read_unlock(mm);
+#ifdef CONFIG_PER_VMA_LOCK
+done:
+#endif
if (likely(!(fault & VM_FAULT_ERROR)))
return;
_
Patches currently in -mm which might be from surenb@xxxxxxxxxx are
mm-introduce-config_per_vma_lock.patch
mm-move-mmap_lock-assert-function-definitions.patch
mm-add-per-vma-lock-and-helper-functions-to-control-it.patch
mm-mark-vma-as-being-written-when-changing-vm_flags.patch
mm-mmap-move-vma_prepare-before-vma_adjust_trans_huge.patch
mm-khugepaged-write-lock-vma-while-collapsing-a-huge-page.patch
mm-mmap-write-lock-vmas-in-vma_prepare-before-modifying-them.patch
mm-mremap-write-lock-vma-while-remapping-it-to-a-new-address-range.patch
mm-write-lock-vmas-before-removing-them-from-vma-tree.patch
mm-conditionally-write-lock-vma-in-free_pgtables.patch
kernel-fork-assert-no-vma-readers-during-its-destruction.patch
mm-mmap-prevent-pagefault-handler-from-racing-with-mmu_notifier-registration.patch
mm-introduce-vma-detached-flag.patch
mm-introduce-lock_vma_under_rcu-to-be-used-from-arch-specific-code.patch
mm-fall-back-to-mmap_lock-if-vma-anon_vma-is-not-yet-set.patch
mm-add-fault_flag_vma_lock-flag.patch
mm-prevent-do_swap_page-from-handling-page-faults-under-vma-lock.patch
mm-prevent-userfaults-to-be-handled-under-per-vma-lock.patch
mm-introduce-per-vma-lock-statistics.patch
x86-mm-try-vma-lock-based-page-fault-handling-first.patch
arm64-mm-try-vma-lock-based-page-fault-handling-first.patch
mm-mmap-free-vm_area_struct-without-call_rcu-in-exit_mmap.patch
mm-separate-vma-lock-from-vm_area_struct.patch
per-vma-locks.patch
