Re: [REGRESSION] amd-pstate doesn't work since v5.18.11

[Oleksandr Natalenko <oleksandr@natalenko.name>]

Hello.

On úterý 12. července 2022 19:50:33 CEST Limonciello, Mario wrote:
> [Public]
> 
> + Ray 
> 
> > -----Original Message-----
> > From: Yuan, Perry <Perry.Yuan@amd.com>
> > Sent: Tuesday, July 12, 2022 12:50
> > To: Oleksandr Natalenko <oleksandr@natalenko.name>; Limonciello, Mario
> > <Mario.Limonciello@amd.com>; linux-kernel@vger.kernel.org
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>; Sasha Levin
> > <sashal@kernel.org>; x86@kernel.org; H. Peter Anvin <hpa@zytor.com>;
> > Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Subject: RE: [REGRESSION] amd-pstate doesn't work since v5.18.11
> > 
> > [AMD Official Use Only - General]
> > 
> > Hi Oleksandr:
> > 
> > > -----Original Message-----
> > > From: Oleksandr Natalenko <oleksandr@natalenko.name>
> > > Sent: Wednesday, July 13, 2022 1:40 AM
> > > To: Limonciello, Mario <Mario.Limonciello@amd.com>; linux-
> > > kernel@vger.kernel.org
> > > Cc: Yuan, Perry <Perry.Yuan@amd.com>; Rafael J. Wysocki
> > > <rafael.j.wysocki@intel.com>; Sasha Levin <sashal@kernel.org>;
> > > x86@kernel.org; H. Peter Anvin <hpa@zytor.com>; Greg Kroah-Hartman
> > > <gregkh@linuxfoundation.org>
> > > Subject: [REGRESSION] amd-pstate doesn't work since v5.18.11
> > >
> > > [CAUTION: External Email]
> > >
> > > Hello Mario.
> > >
> > > The following commits were pulled into v5.18.11:
> > >
> > > ```
> > > $ git log --oneline --no-merges v5.18.10..v5.18.11 | grep ACPI
> > > 2783414e6ef7 ACPI: CPPC: Don't require _OSC if X86_FEATURE_CPPC is
> > > supported
> > > 3068cfeca3b5 ACPI: CPPC: Only probe for _CPC if CPPC v2 is acked
> > > 8beb71759cc8 ACPI: bus: Set CPPC _OSC bits for all and when CPPC_LIB is
> > > supported
> > > 13bb696dd2f3 ACPI: CPPC: Check _OSC for flexible address space ```
> > >
> > > and now this happens:
> > >
> > > ```
> > > $ sudo modprobe amd-pstate shared_mem=1
> > > modprobe: ERROR: could not insert 'amd_pstate': No such device ```
> > >
> > > With v5.18.10 this worked just fine.
> > >
> > > In your upstream commit 8b356e536e69f3a4d6778ae9f0858a1beadabb1f
> > > you write:
> > >
> > > ```
> > > If there is additional breakage on the shared memory designs also missing
> > > this _OSC, additional follow up changes may be needed.
> > > ```
> > >
> > > So the question is what else should be pulled into the stable tree to
> > > unbreak amd-pstate?
> > >
> > > Thanks.
> > >
> > > --
> > > Oleksandr Natalenko (post-factum)
> > >
> > 
> > Could you share the lscpu output ?

Here's my `lscpu`:

```
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Address sizes:                   43 bits physical, 48 bits virtual
Byte Order:                      Little Endian
CPU(s):                          24
On-line CPU(s) list:             0-23
Vendor ID:                       AuthenticAMD
Model name:                      AMD Ryzen 9 3900XT 12-Core Processor
CPU family:                      23
Model:                           113
Thread(s) per core:              2
Core(s) per socket:              12
Socket(s):                       1
Stepping:                        0
Frequency boost:                 enabled
CPU(s) scaling MHz:              59%
CPU max MHz:                     3800,0000
CPU min MHz:                     2200,0000
BogoMIPS:                        7589.71
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 constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 cdp_l3 hw_pstate ssbd mba ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 cqm rdt_a rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr rdpru wbnoinvd arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif v_spec_ctrl umip rdpid overflow_recov succor smca sev sev_es
Virtualization:                  AMD-V
L1d cache:                       384 KiB (12 instances)
L1i cache:                       384 KiB (12 instances)
L2 cache:                        6 MiB (12 instances)
L3 cache:                        64 MiB (4 instances)
NUMA node(s):                    1
NUMA node0 CPU(s):               0-23
Vulnerability Itlb multihit:     Not affected
Vulnerability L1tf:              Not affected
Vulnerability Mds:               Not affected
Vulnerability Meltdown:          Not affected
Vulnerability Mmio stale data:   Not affected
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl
Vulnerability Spectre v1:        Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:        Mitigation; Retpolines, IBPB conditional, STIBP conditional, RSB filling
Vulnerability Srbds:             Not affected
Vulnerability Tsx async abort:   Not affected

```

> > Perry.
> 
> Thanks this is the sort of thing I was worried might happen as a result of requiring
> the _OSC.  It was introduced as part of that commit 8beb71759cc8.
> 
> To solve it I think we need to add more things to cpc_supported_by_cpu
> (https://github.com/torvalds/linux/blob/525496a030de4ae64bb9e1d6bfc88eec6f5fe6e2/arch/x86/kernel/acpi/cppc.c#L19)
> 
> The question is how do we safely detect the shared memory designs?
> These are a fixed quantity as newer designs /should/ be using the MSR.
> 
> I am tending to thing that unfortunately we need to have an allow-list of shared
> memory design here unless someone has other ideas.

Happy to test any patches as needed.

-- 
Oleksandr Natalenko (post-factum)