From: Hugh Dickins The BTS and PEBS buffers both have their virtual addresses programmed into the hardware. This means that any access to them is performed via the page tables. The times that the hardware accesses these are entirely dependent on how the performance monitoring hardware events are set up. In other words, there is no way for the kernel to tell when the hardware might access these buffers. To avoid perf crashes, place 'debug_store' allocate pages and map them into the cpu_entry_area fixmap. The PEBS fixup buffer does not need this treatment. [ tglx: Got rid of the kaiser_add_mapping() cruft ] Signed-off-by: Hugh Dickins Signed-off-by: Dave Hansen Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner Cc: Andy Lutomirski Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Brian Gerst Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: keescook@google.com --- arch/x86/events/intel/ds.c | 114 ++++++++++++++++++++++++++----------------- arch/x86/events/perf_event.h | 2 2 files changed, 73 insertions(+), 43 deletions(-) --- a/arch/x86/events/intel/ds.c +++ b/arch/x86/events/intel/ds.c @@ -280,17 +280,46 @@ void fini_debug_store_on_cpu(int cpu) static DEFINE_PER_CPU(void *, insn_buffer); -static int alloc_pebs_buffer(int cpu) +static u64 ds_update_fixmap(int idx, void *addr, size_t size, pgprot_t prot) { - struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds; + phys_addr_t pa, va; + size_t msz = 0; + + va = __fix_to_virt(idx); + pa = virt_to_phys(addr); + for (; msz < size; idx--, msz += PAGE_SIZE, pa += PAGE_SIZE) + __set_fixmap(idx, pa, prot); + return va; +} + +static void *dsalloc_pages(size_t size, gfp_t flags, int cpu) +{ + unsigned int order = get_order(size); int node = cpu_to_node(cpu); - int max; + struct page *page; + + page = __alloc_pages_node(node, flags | __GFP_ZERO, order); + return page ? page_address(page) : NULL; +} + +static void dsfree_pages(const void *buffer, size_t size) +{ + if (buffer) + free_pages((unsigned long)buffer, get_order(size)); +} + +static int alloc_pebs_buffer(int cpu) +{ + struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu); + struct debug_store *ds = hwev->ds; + size_t bsiz = x86_pmu.pebs_buffer_size; + int idx, max, node = cpu_to_node(cpu); void *buffer, *ibuffer; if (!x86_pmu.pebs) return 0; - buffer = kzalloc_node(x86_pmu.pebs_buffer_size, GFP_KERNEL, node); + buffer = dsalloc_pages(bsiz, GFP_KERNEL, cpu); if (unlikely(!buffer)) return -ENOMEM; @@ -301,25 +330,27 @@ static int alloc_pebs_buffer(int cpu) if (x86_pmu.intel_cap.pebs_format < 2) { ibuffer = kzalloc_node(PEBS_FIXUP_SIZE, GFP_KERNEL, node); if (!ibuffer) { - kfree(buffer); + dsfree_pages(buffer, bsiz); return -ENOMEM; } per_cpu(insn_buffer, cpu) = ibuffer; } - - max = x86_pmu.pebs_buffer_size / x86_pmu.pebs_record_size; - - ds->pebs_buffer_base = (u64)(unsigned long)buffer; + hwev->ds_pebs_vaddr = buffer; + /* Update the fixmap */ + idx = get_cpu_entry_area_index(cpu, cpu_debug_buffers.pebs_buffer); + ds->pebs_buffer_base = ds_update_fixmap(idx, buffer, bsiz, + PAGE_KERNEL); ds->pebs_index = ds->pebs_buffer_base; - ds->pebs_absolute_maximum = ds->pebs_buffer_base + - max * x86_pmu.pebs_record_size; - + max = x86_pmu.pebs_record_size * (bsiz / x86_pmu.pebs_record_size); + ds->pebs_absolute_maximum = ds->pebs_buffer_base + max; return 0; } static void release_pebs_buffer(int cpu) { - struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds; + struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu); + struct debug_store *ds = hwev->ds; + int idx; if (!ds || !x86_pmu.pebs) return; @@ -327,73 +358,70 @@ static void release_pebs_buffer(int cpu) kfree(per_cpu(insn_buffer, cpu)); per_cpu(insn_buffer, cpu) = NULL; - kfree((void *)(unsigned long)ds->pebs_buffer_base); + /* Clear the fixmap */ + idx = get_cpu_entry_area_index(cpu, cpu_debug_buffers.pebs_buffer); + ds_update_fixmap(idx, 0, x86_pmu.pebs_buffer_size, PAGE_NONE); ds->pebs_buffer_base = 0; + dsfree_pages(hwev->ds_pebs_vaddr, x86_pmu.pebs_buffer_size); + hwev->ds_pebs_vaddr = NULL; } static int alloc_bts_buffer(int cpu) { - struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds; - int node = cpu_to_node(cpu); - int max, thresh; + struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu); + struct debug_store *ds = hwev->ds; + int idx, max; void *buffer; if (!x86_pmu.bts) return 0; - buffer = kzalloc_node(BTS_BUFFER_SIZE, GFP_KERNEL | __GFP_NOWARN, node); + buffer = dsalloc_pages(BTS_BUFFER_SIZE, GFP_KERNEL | __GFP_NOWARN, cpu); if (unlikely(!buffer)) { WARN_ONCE(1, "%s: BTS buffer allocation failure\n", __func__); return -ENOMEM; } - - max = BTS_BUFFER_SIZE / BTS_RECORD_SIZE; - thresh = max / 16; - - ds->bts_buffer_base = (u64)(unsigned long)buffer; + hwev->ds_bts_vaddr = buffer; + /* Update the fixmap */ + idx = get_cpu_entry_area_index(cpu, cpu_debug_buffers.bts_buffer); + ds->bts_buffer_base = ds_update_fixmap(idx, buffer, BTS_BUFFER_SIZE, + PAGE_KERNEL); ds->bts_index = ds->bts_buffer_base; - ds->bts_absolute_maximum = ds->bts_buffer_base + - max * BTS_RECORD_SIZE; - ds->bts_interrupt_threshold = ds->bts_absolute_maximum - - thresh * BTS_RECORD_SIZE; - + max = BTS_RECORD_SIZE * (BTS_BUFFER_SIZE / BTS_RECORD_SIZE); + ds->bts_absolute_maximum = ds->bts_buffer_base + max; + ds->bts_interrupt_threshold = ds->bts_absolute_maximum - (max / 16); return 0; } static void release_bts_buffer(int cpu) { - struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds; + struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu); + struct debug_store *ds = hwev->ds; + int idx; if (!ds || !x86_pmu.bts) return; - kfree((void *)(unsigned long)ds->bts_buffer_base); + /* Clear the fixmap */ + idx = get_cpu_entry_area_index(cpu, cpu_debug_buffers.bts_buffer); + ds_update_fixmap(idx, 0, BTS_BUFFER_SIZE, PAGE_NONE); ds->bts_buffer_base = 0; + dsfree_pages(hwev->ds_bts_vaddr, BTS_BUFFER_SIZE); + hwev->ds_bts_vaddr = NULL; } static int alloc_ds_buffer(int cpu) { - int node = cpu_to_node(cpu); - struct debug_store *ds; - - ds = kzalloc_node(sizeof(*ds), GFP_KERNEL, node); - if (unlikely(!ds)) - return -ENOMEM; + struct debug_store *ds = &get_cpu_entry_area(cpu)->cpu_debug_store; + memset(ds, 0, sizeof(*ds)); per_cpu(cpu_hw_events, cpu).ds = ds; - return 0; } static void release_ds_buffer(int cpu) { - struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds; - - if (!ds) - return; - per_cpu(cpu_hw_events, cpu).ds = NULL; - kfree(ds); } void release_ds_buffers(void) --- a/arch/x86/events/perf_event.h +++ b/arch/x86/events/perf_event.h @@ -199,6 +199,8 @@ struct cpu_hw_events { * Intel DebugStore bits */ struct debug_store *ds; + void *ds_pebs_vaddr; + void *ds_bts_vaddr; u64 pebs_enabled; int n_pebs; int n_large_pebs;