Commit bc7996c8 authored by Kefeng Wang's avatar Kefeng Wang Committed by Andrew Morton
Browse files

x86: mm: accelerate pagefault when badaccess 

The access_error() of vma is 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.

Link: https://lkml.kernel.org/r/20240403083805.1818160-8-wangkefeng.wang@huawei.com


Reviewed-by: default avatarSuren Baghdasaryan <surenb@google.com>
Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 82b7a618

arch/x86/mm/fault.c

+14 −9
Original line number Diff line number Diff line
@@ -866,14 +866,17 @@ 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);

}
@@ -897,7 +900,8 @@ 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.
@@ -927,9 +931,9 @@ 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);

	}

}
@@ -1357,8 +1361,9 @@ 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)))
@@ -1394,7 +1399,7 @@ 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;

	}