[PATCH v3 19/20] x86/mm: Add speculative pagefault handling
From: Laurent Dufour <hidden>
Date: 2017-09-08 18:08:30
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/include/asm/pgtable_types.h | 7 +++++++ arch/x86/mm/fault.c | 19 +++++++++++++++++++ 2 files changed, 26 insertions(+)
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index f1492473f10e..aadc8ecb91fb 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h@@ -257,6 +257,13 @@ enum page_cache_mode { #define PGD_IDENT_ATTR 0x001 /* PRESENT (no other attributes) */ #endif +/* + * Advertise that we call the Speculative Page Fault handler. + */ +#ifdef CONFIG_X86_64 +#define __HAVE_ARCH_CALL_SPF +#endif + #ifdef CONFIG_X86_32 # include <asm/pgtable_32_types.h> #else
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index b836a7274e12..652af5524f42 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c@@ -1365,6 +1365,24 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, if (error_code & PF_INSTR) flags |= FAULT_FLAG_INSTRUCTION; +#ifdef __HAVE_ARCH_CALL_SPF + 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)) { + perf_sw_event(PERF_COUNT_SW_SPF, 1, + regs, address); + goto done; + } + } +#endif /* __HAVE_ARCH_CALL_SPF */ + /* * When running in the kernel we expect faults to occur only to * addresses in user space. All other faults represent errors in
@@ -1474,6 +1492,7 @@ __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.
--
2.7.4