[PATCH v4 29/33] x86/mm: try VMA lock-based page fault handling first
From: Suren Baghdasaryan <surenb@google.com>
Date: 2023-02-27 17:39:10
Also in:
linux-mm, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 mm · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra
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@google.com> --- 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 a825bf031f49..df21fba77db1 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..e4399983c50c 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)) + 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;
--
2.39.2.722.g9855ee24e9-goog