[PATCH 09/16] x86/mm: Add speculative pagefault handling
From: Laurent Dufour <hidden>
Date: 2017-08-08 14:36:23
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
From: Peter Zijlstra <peterz@infradead.org> Try a speculative fault before acquiring mmap_sem, if it returns with VM_FAULT_RETRY continue with the mmap_sem acquisition and do the traditional fault. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> [Clearing of FAULT_FLAG_ALLOW_RETRY is now done in handle_speculative_fault()] [Retry with usual fault path in the case VM_ERROR is returned by handle_speculative_fault(). This allows signal to be delivered] Signed-off-by: Laurent Dufour <redacted> --- arch/x86/mm/fault.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 2a1fa10c6a98..46fb9c2a832d 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c@@ -1365,6 +1365,19 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, if (error_code & PF_INSTR) flags |= FAULT_FLAG_INSTRUCTION; + if (error_code & PF_USER) { + fault = handle_speculative_fault(mm, address, flags); + + /* + * We also check against VM_FAULT_ERROR because we have to + * raise a signal by calling later mm_fault_error() which + * requires the vma pointer to be set. So in that case, + * we fall through the normal path. + */ + if (!(fault & VM_FAULT_RETRY || fault & VM_FAULT_ERROR)) + goto done; + } + /* * When running in the kernel we expect faults to occur only to * addresses in user space. All other faults represent errors in
@@ -1474,6 +1487,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, return; } +done: /* * Major/minor page fault accounting. If any of the events * returned VM_FAULT_MAJOR, we account it as a major fault.
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2.7.4