Commit 5fafc438 authored by Kefeng Wang's avatar Kefeng Wang Committed by Peng Zhang
Browse files

x86: mm: accelerate pagefault when badaccess 

maillist inclusion
category: performance
bugzilla: https://gitee.com/openeuler/kernel/issues/I9E07B
CVE: NA

Reference: https://lore.kernel.org/linux-mm/20240403083805.1818160-1-wangkefeng.wang@huawei.com/



--------------------------------

The access_error() of vma already checked under per-VMA lock, if it
is a bad access, directly handle error, no need to retry with mmap_lock
again. In order to release the correct lock, pass the mm_struct into
bad_area_access_error(), if mm is NULL, release vma lock, or release
mmap_lock. Since the page faut is handled under per-VMA lock, count it
as a vma lock event with VMA_LOCK_SUCCESS.

Reviewed-by: default avatarSuren Baghdasaryan <surenb@google.com>
Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: default avatarZhangPeng <zhangpeng362@huawei.com>
parent 67c3cd13

arch/x86/mm/fault.c

+14 −9
Original line number Diff line number Diff line
@@ -868,14 +868,17 @@ bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 


static void

__bad_area(struct pt_regs *regs, unsigned long error_code,

	   unsigned long address, u32 pkey, int si_code)

	   unsigned long address, struct mm_struct *mm,

	   struct vm_area_struct *vma, u32 pkey, int si_code)

{

	struct mm_struct *mm = current->mm;

	/*

	 * Something tried to access memory that isn't in our memory map..

	 * Fix it, but check if it's kernel or user first..

	 */

	if (mm)

		mmap_read_unlock(mm);

	else

		vma_end_read(vma);



	__bad_area_nosemaphore(regs, error_code, address, pkey, si_code);

}
@@ -899,7 +902,8 @@ static inline bool bad_area_access_from_pkeys(unsigned long error_code, 


static noinline void

bad_area_access_error(struct pt_regs *regs, unsigned long error_code,

		      unsigned long address, struct vm_area_struct *vma)

		      unsigned long address, struct mm_struct *mm,

		      struct vm_area_struct *vma)

{

	/*

	 * This OSPKE check is not strictly necessary at runtime.
@@ -929,9 +933,9 @@ bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 
		 */

		u32 pkey = vma_pkey(vma);



		__bad_area(regs, error_code, address, pkey, SEGV_PKUERR);

		__bad_area(regs, error_code, address, mm, vma, pkey, SEGV_PKUERR);

	} else {

		__bad_area(regs, error_code, address, 0, SEGV_ACCERR);

		__bad_area(regs, error_code, address, mm, vma, 0, SEGV_ACCERR);

	}

}
@@ -1358,8 +1362,9 @@ void do_user_addr_fault(struct pt_regs *regs, 
		goto lock_mmap;



	if (unlikely(access_error(error_code, vma))) {

		vma_end_read(vma);

		goto lock_mmap;

		bad_area_access_error(regs, error_code, address, NULL, vma);

		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);

		return;

	}

	fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);

	if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
@@ -1395,7 +1400,7 @@ void do_user_addr_fault(struct pt_regs *regs, 
	 * we can handle it..

	 */

	if (unlikely(access_error(error_code, vma))) {

		bad_area_access_error(regs, error_code, address, vma);

		bad_area_access_error(regs, error_code, address, mm, vma);

		return;

	}