From 5dfaf90f8052327c92fbe3c470a2e6634be296c0 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 16 Jun 2009 10:23:32 +0200 Subject: x86: mm: Read cr2 before prefetching the mmap_lock Prefetch instructions can generate spurious faults on certain models of older CPUs. The faults themselves cannot be stopped and they can occur pretty much anywhere - so the way we solve them is that we detect certain patterns and ignore the fault. There is one small path of code where we must not take faults though: the #PF handler execution leading up to the reading of the CR2 (the faulting address). If we take a fault there then we destroy the CR2 value (with that of the prefetching instruction's) and possibly mishandle user-space or kernel-space pagefaults. It turns out that in current upstream we do exactly that: prefetchw(&mm->mmap_sem); /* Get the faulting address: */ address = read_cr2(); This is not good. So turn around the order: first read the cr2 then prefetch the lock address. Reading cr2 is plenty fast (2 cycles) so delaying the prefetch by this amount shouldnt be a big issue performance-wise. [ And this might explain a mystery fault.c warning that sometimes occurs on one an old AMD/Semptron based test-system i have - which does have such prefetch problems. ] Cc: Mathieu Desnoyers Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Nick Piggin Cc: Pekka Enberg Cc: Vegard Nossum Cc: Jeremy Fitzhardinge Cc: Hugh Dickins LKML-Reference: <20090616030522.GA22162@Krystal> Signed-off-by: Ingo Molnar --- arch/x86/mm/fault.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/x86/mm/fault.c') diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index c6acc6326374..0482fa649738 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -951,11 +951,11 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code) tsk = current; mm = tsk->mm; - prefetchw(&mm->mmap_sem); - /* Get the faulting address: */ address = read_cr2(); + prefetchw(&mm->mmap_sem); + if (unlikely(kmmio_fault(regs, address))) return; -- cgit v1.2.3 From d06063cc221fdefcab86589e79ddfdb7c0e14b63 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 10 Apr 2009 09:01:23 -0700 Subject: Move FAULT_FLAG_xyz into handle_mm_fault() callers This allows the callers to now pass down the full set of FAULT_FLAG_xyz flags to handle_mm_fault(). All callers have been (mechanically) converted to the new calling convention, there's almost certainly room for architectures to clean up their code and then add FAULT_FLAG_RETRY when that support is added. Signed-off-by: Linus Torvalds --- arch/x86/mm/fault.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/mm/fault.c') diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index c403526d5d15..78a5fff857be 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1113,7 +1113,7 @@ good_area: * make sure we exit gracefully rather than endlessly redo * the fault: */ - fault = handle_mm_fault(mm, vma, address, write); + fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0); if (unlikely(fault & VM_FAULT_ERROR)) { mm_fault_error(regs, error_code, address, fault); -- cgit v1.2.3 From ad361c9884e809340f6daca80d56a9e9c871690a Mon Sep 17 00:00:00 2001 From: Joe Perches Date: Mon, 6 Jul 2009 13:05:40 -0700 Subject: Remove multiple KERN_ prefixes from printk formats Commit 5fd29d6ccbc98884569d6f3105aeca70858b3e0f ("printk: clean up handling of log-levels and newlines") changed printk semantics. printk lines with multiple KERN_ prefixes are no longer emitted as before the patch. is now included in the output on each additional use. Remove all uses of multiple KERN_s in formats. Signed-off-by: Joe Perches Signed-off-by: Linus Torvalds --- arch/x86/mm/fault.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'arch/x86/mm/fault.c') diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 78a5fff857be..85307cc6e45f 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -426,10 +426,11 @@ static noinline int vmalloc_fault(unsigned long address) } static const char errata93_warning[] = -KERN_ERR "******* Your BIOS seems to not contain a fix for K8 errata #93\n" -KERN_ERR "******* Working around it, but it may cause SEGVs or burn power.\n" -KERN_ERR "******* Please consider a BIOS update.\n" -KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n"; +KERN_ERR +"******* Your BIOS seems to not contain a fix for K8 errata #93\n" +"******* Working around it, but it may cause SEGVs or burn power.\n" +"******* Please consider a BIOS update.\n" +"******* Disabling USB legacy in the BIOS may also help.\n"; /* * No vm86 mode in 64-bit mode: -- cgit v1.2.3 From a1a08d1cb0ab148fd74216e4c0b4d4db18fe62c6 Mon Sep 17 00:00:00 2001 From: Roland Dreier Date: Sat, 11 Jul 2009 00:10:04 -0700 Subject: x86: Remove spurious printk level from segfault message Since commit 5fd29d6c ("printk: clean up handling of log-levels and newlines"), the kernel logs segfaults like: <6>gnome-power-man[24509]: segfault at 20 ip 00007f9d4950465a sp 00007fffbb50fc70 error 4 in libgobject-2.0.so.0.2103.0[7f9d494f7000+45000] with the extra "<6>" being KERN_INFO. This happens because the printk in show_signal_msg() started with KERN_CONT and then used "%s" to pass in the real level; and KERN_CONT is no longer an empty string, and printk only pays attention to the level at the very beginning of the format string. Therefore, remove the KERN_CONT from this printk, since it is now actively causing problems (and never really made any sense). Signed-off-by: Roland Dreier Cc: Linus Torvalds LKML-Reference: <874otjitkj.fsf@shaolin.home.digitalvampire.org> Signed-off-by: Ingo Molnar --- arch/x86/mm/fault.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/mm/fault.c') diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 85307cc6e45f..bfae139182ff 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -697,7 +697,7 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code, if (!printk_ratelimit()) return; - printk(KERN_CONT "%s%s[%d]: segfault at %lx ip %p sp %p error %lx", + printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx", task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, tsk->comm, task_pid_nr(tsk), address, (void *)regs->ip, (void *)regs->sp, error_code); -- cgit v1.2.3