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Violators will be prosecuted for from ; Tue, 13 Mar 2018 18:00:54 -0000 From: Laurent Dufour Subject: [PATCH v9 23/24] x86/mm: Add speculative pagefault handling Date: Tue, 13 Mar 2018 18:59:53 +0100 In-Reply-To: <1520963994-28477-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1520963994-28477-1-git-send-email-ldufour@linux.vnet.ibm.com> Message-Id: <1520963994-28477-24-git-send-email-ldufour@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: paulmck@linux.vnet.ibm.com, peterz@infradead.org, akpm@linux-foundation.org, kirill@shutemov.name, ak@linux.intel.com, mhocko@kernel.org, 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 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, 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 to the VMA fetch during the speculative path in case of retry] Signed-off-by: Laurent Dufour --- arch/x86/mm/fault.c | 38 +++++++++++++++++++++++++++++++++++++- 1 file changed, 37 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index e6af2b464c3d..a73cf227edd6 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1239,6 +1239,9 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address) { struct vm_area_struct *vma; +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT + struct vm_area_struct *spf_vma = NULL; +#endif struct task_struct *tsk; struct mm_struct *mm; int fault, major = 0; @@ -1332,6 +1335,27 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, if (error_code & X86_PF_INSTR) flags |= FAULT_FLAG_INSTRUCTION; +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT + if ((error_code & X86_PF_USER) && (atomic_read(&mm->mm_users) > 1)) { + fault = handle_speculative_fault(mm, address, flags, + &spf_vma); + + if (!(fault & VM_FAULT_RETRY)) { + if (!(fault & VM_FAULT_ERROR)) { + perf_sw_event(PERF_COUNT_SW_SPF, 1, + regs, address); + goto done; + } + /* + * In case of error we need the pkey value, but + * can't get it from the spf_vma as it is only returned + * when VM_FAULT_RETRY is returned. So we have to + * retry the page fault with the mmap_sem grabbed. + */ + } + } +#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */ + /* * When running in the kernel we expect faults to occur only to * addresses in user space. All other faults represent errors in @@ -1365,7 +1389,16 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, might_sleep(); } - vma = find_vma(mm, address); +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT + if (spf_vma) { + if (can_reuse_spf_vma(spf_vma, address)) + vma = spf_vma; + else + vma = find_vma(mm, address); + spf_vma = NULL; + } else +#endif + vma = find_vma(mm, address); if (unlikely(!vma)) { bad_area(regs, error_code, address); return; @@ -1451,6 +1484,9 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code, return; } +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT +done: +#endif /* * Major/minor page fault accounting. If any of the events * returned VM_FAULT_MAJOR, we account it as a major fault. -- 2.7.4