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Violators will be prosecuted for from ; Tue, 17 Apr 2018 15:35:01 +0100 From: Laurent Dufour Subject: [PATCH v10 24/25] x86/mm: add speculative pagefault handling Date: Tue, 17 Apr 2018 16:33:30 +0200 In-Reply-To: <1523975611-15978-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1523975611-15978-1-git-send-email-ldufour@linux.vnet.ibm.com> Message-Id: <1523975611-15978-25-git-send-email-ldufour@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, mhocko@kernel.org, peterz@infradead.org, kirill@shutemov.name, ak@linux.intel.com, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky , Andrea Arcangeli , Alexei Starovoitov , kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com, Daniel Jordan , David Rientjes , Jerome Glisse , Ganesh Mahendran Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, paulmck@linux.vnet.ibm.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org From: Peter Zijlstra 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) [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] [Try speculative fault path only for multi threaded processes] [Try reuse to the VMA fetch during the speculative path in case of retry] [Call reuse_spf_or_find_vma()] [Handle memory protection key fault] Signed-off-by: Laurent Dufour --- arch/x86/mm/fault.c | 42 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 38 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 73bd8c95ac71..59f778386df5 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1220,7 +1220,7 @@ __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; @@ -1310,6 +1310,30 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, flags |= FAULT_FLAG_INSTRUCTION; /* + * Do not try speculative page fault for kernel's pages and if + * the fault was due to protection keys since it can't be resolved. + */ + if (IS_ENABLED(CONFIG_SPECULATIVE_PAGE_FAULT) && + !(error_code & X86_PF_PK)) { + fault = handle_speculative_fault(mm, address, flags, &vma); + 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; + } + } else { + vma = NULL; + } + + /* * 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 @@ -1342,7 +1366,8 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, might_sleep(); } - vma = find_vma(mm, address); + if (!vma || !can_reuse_spf_vma(vma, address)) + vma = find_vma(mm, address); if (unlikely(!vma)) { bad_area(regs, error_code, address); return; @@ -1409,8 +1434,15 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, if (flags & FAULT_FLAG_ALLOW_RETRY) { flags &= ~FAULT_FLAG_ALLOW_RETRY; flags |= FAULT_FLAG_TRIED; - if (!fatal_signal_pending(tsk)) + if (!fatal_signal_pending(tsk)) { + /* + * Do not try to reuse this vma and fetch it + * again since we will release the mmap_sem. + */ + if (IS_ENABLED(CONFIG_SPECULATIVE_PAGE_FAULT)) + vma = NULL; goto retry; + } } /* User mode? Just return to handle the fatal exception */ @@ -1423,8 +1455,10 @@ __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