Messages in this thread | | | From | "Limonciello, Mario" <> | Subject | RE: [REGRESSION] amd-pstate doesn't work since v5.18.11 | Date | Tue, 12 Jul 2022 17:50:33 +0000 |
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[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 ? > > 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.
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