Re: [PATCH] x86/oprofile/ppro: Do not use __this_cpu* accessors in preemptible context

From: Borislav Petkov
Date: Wed Nov 08 2017 - 06:24:49 EST


On Wed, Nov 08, 2017 at 11:48:28AM +0100, Thomas Gleixner wrote:
> AFAICT, ppro_setup_ctrs() has the same issue

Here's an updated patch:

---
From: Borislav Petkov <bp@xxxxxxx>
Date: Tue, 7 Nov 2017 18:20:50 +0100
Subject: [PATCH] x86/oprofile/ppro: Do not use __this_cpu* accessors in preemptible context

The warning below says it all. And we should not have used those
accessors in the first place: it is PPro so no mixed silicon revisions
and thus can simply use boot_cpu_data.

BUG: using __this_cpu_read() in preemptible [00000000] code: swapper/0/1
caller is __this_cpu_preempt_check
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.14.0-rc8 #4
Call Trace:
dump_stack
check_preemption_disabled
? do_early_param
__this_cpu_preempt_check
arch_perfmon_init
op_nmi_init
? alloc_pci_root_info
oprofile_arch_init
oprofile_init
do_one_initcall
...


Fix the other callsite in ppro_setup_ctrs() too, while at it.

Reported-and-tested-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Fix-creation-mandated-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Robert Richter <rric@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
---
arch/x86/oprofile/op_model_ppro.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/oprofile/op_model_ppro.c b/arch/x86/oprofile/op_model_ppro.c
index 350f7096baac..488b2efb24b9 100644
--- a/arch/x86/oprofile/op_model_ppro.c
+++ b/arch/x86/oprofile/op_model_ppro.c
@@ -84,8 +84,8 @@ static void ppro_setup_ctrs(struct op_x86_model_spec const *model,
* counter width:
*/
if (!(eax.split.version_id == 0 &&
- __this_cpu_read(cpu_info.x86) == 6 &&
- __this_cpu_read(cpu_info.x86_model) == 15)) {
+ boot_cpu_data.x86 == 6 &&
+ boot_cpu_data.x86_model == 15)) {

if (counter_width < eax.split.bit_width)
counter_width = eax.split.bit_width;
@@ -212,8 +212,9 @@ static void arch_perfmon_setup_counters(void)
eax.full = cpuid_eax(0xa);

/* Workaround for BIOS bugs in 6/15. Taken from perfmon2 */
- if (eax.split.version_id == 0 && __this_cpu_read(cpu_info.x86) == 6 &&
- __this_cpu_read(cpu_info.x86_model) == 15) {
+ if (eax.split.version_id == 0 &&
+ boot_cpu_data.x86 == 6 &&
+ boot_cpu_data.x86_model == 15) {
eax.split.version_id = 2;
eax.split.num_counters = 2;
eax.split.bit_width = 40;
--
2.13.0

SUSE Linux GmbH, GF: Felix ImendÃrffer, Jane Smithard, Graham Norton, HRB 21284 (AG NÃrnberg)
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