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

[Bernhard Held]

On 05/30/2017 at 07:59 PM, 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 part of the patch is not required anyway, so I will resubmit the
> patch with this part disabled (and with an added call to
> init_cache_modes() as Andy suggested).
>
> Mikulas
>
> > > 3. use the full PAT patch and apply the below patch on the top of it.
> >
> > No joy.

Same result here., only #2 boots.

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 23
model name      : Intel(R) Xeon(R) CPU           E5450  @ 3.00GHz
stepping        : 10
microcode       : 0xa0b
cpu MHz         : 2000.000
cache size      : 6144 KB
physical id     : 0
siblings        : 4
core id         : 0
cpu cores       : 4
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
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 lm constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 xsave lahf_lm tpr_shadow vnmi flexpriority dtherm
bugs            :
bogomips        : 5999.70
clflush size    : 64
cache_alignment : 64
address sizes   : 38 bits physical, 48 bits virtual
power management:

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 23
model name      : Intel(R) Xeon(R) CPU           E5450  @ 3.00GHz
stepping        : 10
microcode       : 0xa0b
cpu MHz         : 2000.000
cache size      : 6144 KB
physical id     : 0
siblings        : 4
core id         : 3
cpu cores       : 4
apicid          : 3
initial apicid  : 3
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
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 lm constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 xsave lahf_lm tpr_shadow vnmi flexpriority dtherm
bugs            :
bogomips        : 5999.98
clflush size    : 64
cache_alignment : 64
address sizes   : 38 bits physical, 48 bits virtual
power management:

processor       : 2
vendor_id       : GenuineIntel
cpu family      : 6
model           : 23
model name      : Intel(R) Xeon(R) CPU           E5450  @ 3.00GHz
stepping        : 10
microcode       : 0xa0b
cpu MHz         : 2000.000
cache size      : 6144 KB
physical id     : 0
siblings        : 4
core id         : 2
cpu cores       : 4
apicid          : 2
initial apicid  : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
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 lm constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 xsave lahf_lm tpr_shadow vnmi flexpriority dtherm
bugs            :
bogomips        : 5900.00
clflush size    : 64
cache_alignment : 64
address sizes   : 38 bits physical, 48 bits virtual
power management:

processor       : 3
vendor_id       : GenuineIntel
cpu family      : 6
model           : 23
model name      : Intel(R) Xeon(R) CPU           E5450  @ 3.00GHz
stepping        : 10
microcode       : 0xa0b
cpu MHz         : 2000.000
cache size      : 6144 KB
physical id     : 0
siblings        : 4
core id         : 1
cpu cores       : 4
apicid          : 1
initial apicid  : 1
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
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 lm constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 xsave lahf_lm tpr_shadow vnmi flexpriority dtherm
bugs            :
bogomips        : 5999.98
clflush size    : 64
cache_alignment : 64
address sizes   : 38 bits physical, 48 bits virtual
power management:

Cheers,
Bernhard