linux-kernel - Re: [PATCH 1/1] Fix int1 recursion when no perf_bp

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Message-ID: <CAO6TR8UOX4k7sQHXYY+Tx9jsQeWu3m=a8mz+yT812Pcgq0k8Mg@mail.gmail.com>
Date:	Thu, 10 Dec 2015 14:11:56 -0700
From:	Jeff Merkey <linux.mdb@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Andy Lutomirski <luto@...capital.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>, Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH 1/1] Fix int1 recursion when no perf_bp_event is registeredy

There's no output to send when the bug occurs, the system locks up.
Here is the CPU info in any event for the affected system.

processor	: 0
vendor_id	: AuthenticAMD
cpu family	: 16
model		: 2
model name	: AMD Phenom(tm) 9850 Quad-Core Processor
stepping	: 3
microcode	: 0x1000095
cpu MHz		: 1250.000
cache size	: 512 KB
physical id	: 0
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 5
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nopl
nonstop_tsc extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm
extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs
hw_pstate npt lbrv svm_lock vmmcall
bugs		: tlb_mmatch fxsave_leak sysret_ss_attrs
bogomips	: 5022.82
TLB size	: 1024 4K pages
clflush size	: 64
cache_alignment	: 64
address sizes	: 48 bits physical, 48 bits virtual
power management: ts ttp tm stc 100mhzsteps hwpstate

processor	: 1
vendor_id	: AuthenticAMD
cpu family	: 16
model		: 2
model name	: AMD Phenom(tm) 9850 Quad-Core Processor
stepping	: 3
microcode	: 0x1000095
cpu MHz		: 1250.000
cache size	: 512 KB
physical id	: 0
siblings	: 4
core id		: 1
cpu cores	: 4
apicid		: 1
initial apicid	: 1
fpu		: yes
fpu_exception	: yes
cpuid level	: 5
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nopl
nonstop_tsc extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm
extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs
hw_pstate npt lbrv svm_lock vmmcall
bugs		: tlb_mmatch fxsave_leak sysret_ss_attrs
bogomips	: 5022.82
TLB size	: 1024 4K pages
clflush size	: 64
cache_alignment	: 64
address sizes	: 48 bits physical, 48 bits virtual
power management: ts ttp tm stc 100mhzsteps hwpstate

processor	: 2
vendor_id	: AuthenticAMD
cpu family	: 16
model		: 2
model name	: AMD Phenom(tm) 9850 Quad-Core Processor
stepping	: 3
microcode	: 0x1000095
cpu MHz		: 1250.000
cache size	: 512 KB
physical id	: 0
siblings	: 4
core id		: 2
cpu cores	: 4
apicid		: 2
initial apicid	: 2
fpu		: yes
fpu_exception	: yes
cpuid level	: 5
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nopl
nonstop_tsc extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm
extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs
hw_pstate npt lbrv svm_lock vmmcall
bugs		: tlb_mmatch fxsave_leak sysret_ss_attrs
bogomips	: 5022.82
TLB size	: 1024 4K pages
clflush size	: 64
cache_alignment	: 64
address sizes	: 48 bits physical, 48 bits virtual
power management: ts ttp tm stc 100mhzsteps hwpstate

processor	: 3
vendor_id	: AuthenticAMD
cpu family	: 16
model		: 2
model name	: AMD Phenom(tm) 9850 Quad-Core Processor
stepping	: 3
microcode	: 0x1000095
cpu MHz		: 1250.000
cache size	: 512 KB
physical id	: 0
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 3
initial apicid	: 3
fpu		: yes
fpu_exception	: yes
cpuid level	: 5
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nopl
nonstop_tsc extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm
extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs
hw_pstate npt lbrv svm_lock vmmcall
bugs		: tlb_mmatch fxsave_leak sysret_ss_attrs
bogomips	: 5022.82
TLB size	: 1024 4K pages
clflush size	: 64
cache_alignment	: 64
address sizes	: 48 bits physical, 48 bits virtual
power management: ts ttp tm stc 100mhzsteps hwpstate



On 12/10/15, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Thu, 10 Dec 2015, Andy Lutomirski wrote:
>> On brief inspection, this smells like a microcode bug.  Can you send
>> /proc/cpuinfo output?
>>
>> If this is the issue, I'm not sure we want to be in the business of
>> working around localized microcode bugs and, if we do, then I think we
>> should explicitly detect the bug and log about it.
>
> I think we should handle such stuff gracefully. Yes, we should log it
> and we also should check what the contents of the debug registers are.
>
> If dr7 has a break point enabled w/o perf having one installed then we
> know that someone did a horrible hackery ....
>
> Thanks,
>
> 	tglx
>
>
>
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