linux-kernel - Re: [tip:x86/urgent] x86/PAT: Fix Xorg regression on CPUs that don't support PAT

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Date:   Tue, 30 May 2017 20:47:03 +0200
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Bernhard Held <berny156@....de>, Andy Lutomirski <luto@...nel.org>,
        Toshi Kani <toshi.kani@...com>, Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "Luis R. Rodriguez" <mcgrof@...e.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [tip:x86/urgent] x86/PAT: Fix Xorg regression on CPUs that don't
 support PAT

On Tue, May 30, 2017 at 01:59:41PM -0400, Mikulas Patocka wrote:
> On Tue, 30 May 2017, Dominik Brodowski wrote:
> 
> > Same boot problem here (Intel(R) Core(TM) i5-5200U CPU on a Dell XPS 13),
> > git-bisected to the same patch...
> > 
> > On Mon, May 29, 2017 at 06:50:57PM -0400, Mikulas Patocka wrote:
> > > Please do the following three tests and test if the kernel boots.
> > > 
> > > 1. use the PAT patch and revert the change to the function pat_enabled()
> > > - i.e. change it to the original:
> > > bool pat_enabled(void)
> > > {
> > > 	return !!__pat_enabled;
> > > }
> > 
> > No joy.
> > 
> > > 2. use the PAT patch and revert the change to the function pat_ap_init
> > > - i.e. change it to the original:
> > > static void pat_ap_init(u64 pat)
> > > {
> > > 	if (!boot_cpu_has(X86_FEATURE_PAT)) {
> > 
> > Joy.
> 
> It is interesting - does it mean that the boot cpu does have PAT and the 
> secondary CPUs don't? Please send /proc/cpuinfo with all the cores active.

This physical CPU has PAT on all cores / siblings:

processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 61
model name	: Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
stepping	: 4
microcode	: 0x24
cpu MHz		: 800.158
cache size	: 3072 KB
physical id	: 0
siblings	: 4
core id		: 0
cpu cores	: 2
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 20
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb intel_pt tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid rdseed adx smap xsaveopt dtherm ida arat pln pts
bugs		:
bogomips	: 4389.80
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

processor	: 1
vendor_id	: GenuineIntel
cpu family	: 6
model		: 61
model name	: Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
stepping	: 4
microcode	: 0x24
cpu MHz		: 800.158
cache size	: 3072 KB
physical id	: 0
siblings	: 4
core id		: 1
cpu cores	: 2
apicid		: 2
initial apicid	: 2
fpu		: yes
fpu_exception	: yes
cpuid level	: 20
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb intel_pt tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid rdseed adx smap xsaveopt dtherm ida arat pln pts
bugs		:
bogomips	: 4436.14
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

processor	: 2
vendor_id	: GenuineIntel
cpu family	: 6
model		: 61
model name	: Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
stepping	: 4
microcode	: 0x24
cpu MHz		: 800.024
cache size	: 3072 KB
physical id	: 0
siblings	: 4
core id		: 0
cpu cores	: 2
apicid		: 1
initial apicid	: 1
fpu		: yes
fpu_exception	: yes
cpuid level	: 20
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb intel_pt tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid rdseed adx smap xsaveopt dtherm ida arat pln pts
bugs		:
bogomips	: 4397.30
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

processor	: 3
vendor_id	: GenuineIntel
cpu family	: 6
model		: 61
model name	: Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
stepping	: 4
microcode	: 0x24
cpu MHz		: 799.890
cache size	: 3072 KB
physical id	: 0
siblings	: 4
core id		: 1
cpu cores	: 2
apicid		: 3
initial apicid	: 3
fpu		: yes
fpu_exception	: yes
cpuid level	: 20
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb intel_pt tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid rdseed adx smap xsaveopt dtherm ida arat pln pts
bugs		:
bogomips	: 4396.84
clflush size	: 64
cache_alignment	: 64
address sizes	: 39 bits physical, 48 bits virtual
power management:

Best,
	Dominik

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