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x86/events/intel/ds: Map debug buffers in cpu_entry_area
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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.

The PEBS fixup buffer does not need this treatment.

[ tglx: Got rid of the kaiser_add_mapping() complication ]

Signed-off-by: Hugh Dickins <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: David Laight <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Greg KH <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>
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Hugh Dickins authored and Ingo Molnar committed Dec 23, 2017
1 parent 10043e0 commit c1961a4
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Showing 2 changed files with 82 additions and 45 deletions.
125 changes: 80 additions & 45 deletions arch/x86/events/intel/ds.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include <linux/types.h>
#include <linux/slab.h>

#include <asm/cpu_entry_area.h>
#include <asm/perf_event.h>
#include <asm/insn.h>

Expand Down Expand Up @@ -280,17 +281,52 @@ void fini_debug_store_on_cpu(int cpu)

static DEFINE_PER_CPU(void *, insn_buffer);

static int alloc_pebs_buffer(int cpu)
static void ds_update_cea(void *cea, void *addr, size_t size, pgprot_t prot)
{
struct debug_store *ds = per_cpu(cpu_hw_events, cpu).ds;
phys_addr_t pa;
size_t msz = 0;

pa = virt_to_phys(addr);
for (; msz < size; msz += PAGE_SIZE, pa += PAGE_SIZE, cea += PAGE_SIZE)
cea_set_pte(cea, pa, prot);
}

static void ds_clear_cea(void *cea, size_t size)
{
size_t msz = 0;

for (; msz < size; msz += PAGE_SIZE, cea += PAGE_SIZE)
cea_set_pte(cea, 0, PAGE_NONE);
}

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;
void *buffer, *ibuffer;
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 max, node = cpu_to_node(cpu);
void *buffer, *ibuffer, *cea;

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;

Expand All @@ -301,99 +337,98 @@ 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 cpu entry area mapping */
cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.pebs_buffer;
ds->pebs_buffer_base = (unsigned long) cea;
ds_update_cea(cea, 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;
void *cea;

if (!ds || !x86_pmu.pebs)
return;

kfree(per_cpu(insn_buffer, cpu));
per_cpu(insn_buffer, cpu) = NULL;

kfree((void *)(unsigned long)ds->pebs_buffer_base);
/* Clear the fixmap */
cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.pebs_buffer;
ds_clear_cea(cea, x86_pmu.pebs_buffer_size);
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;
void *buffer;
struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu);
struct debug_store *ds = hwev->ds;
void *buffer, *cea;
int max;

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 */
cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.bts_buffer;
ds->bts_buffer_base = (unsigned long) cea;
ds_update_cea(cea, 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;
void *cea;

if (!ds || !x86_pmu.bts)
return;

kfree((void *)(unsigned long)ds->bts_buffer_base);
/* Clear the fixmap */
cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.bts_buffer;
ds_clear_cea(cea, BTS_BUFFER_SIZE);
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)
Expand Down
2 changes: 2 additions & 0 deletions arch/x86/events/perf_event.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down

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