[PATCH v11 24/26] x86/mm: add speculative pagefault handling
From: Laurent Dufour <hidden>
Date: 2018-05-17 11:08:18
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] [Don't build SPF call if !CONFIG_SPECULATIVE_PAGE_FAULT] [Handle memory protection key fault] Signed-off-by: Laurent Dufour <redacted> --- arch/x86/mm/fault.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index fd84edf82252..11944bfc805a 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c@@ -1224,7 +1224,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, struct mm_struct *mm; int fault, major = 0; unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; - u32 pkey; + u32 pkey, *pt_pkey = &pkey; tsk = current; mm = tsk->mm;
@@ -1314,6 +1314,27 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, flags |= FAULT_FLAG_INSTRUCTION; /* + * Do not try to do a speculative page fault if the fault was due to + * protection keys since it can't be resolved. + */ + if (!(error_code & X86_PF_PK)) { + fault = handle_speculative_fault(mm, address, flags); + if (fault != VM_FAULT_RETRY) { + perf_sw_event(PERF_COUNT_SW_SPF, 1, regs, address); + /* + * Do not advertise for the pkey value since we don't + * know it. + * This is not a matter as we checked for X86_PF_PK + * earlier, so we should not handle pkey fault here, + * but to be sure that mm_fault_error() callees will + * not try to use it, we invalidate the pointer. + */ + pt_pkey = NULL; + goto done; + } + } + + /* * When running in the kernel we expect faults to occur only to * addresses in user space. All other faults represent errors in * the kernel and should generate an OOPS. Unfortunately, in the
@@ -1427,8 +1448,10 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, } up_read(&mm->mmap_sem); + +done: if (unlikely(fault & VM_FAULT_ERROR)) { - mm_fault_error(regs, error_code, address, &pkey, fault); + mm_fault_error(regs, error_code, address, pt_pkey, fault); return; }
--
2.7.4