linux-kernel - Re: [PATCH v1 1/4] xen/acpi: upload power and performance related data from a PVH dom0

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Message-ID: <fc2ef8da-62e8-431a-8a1b-508b3f9d5ef4@suse.com>
Date: Wed, 4 Dec 2024 09:29:58 +0100
From: Jürgen Groß <jgross@...e.com>
To: Penny Zheng <Penny.Zheng@....com>,
 Stefano Stabellini <sstabellini@...nel.org>,
 Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Cc: Ray Huang <Ray.Huang@....com>, Xenia Ragiadakou
 <Xenia.Ragiadakou@....com>, Jason Andryuk <jason.andryuk@....com>,
 xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
 Roger Pau Monné <roger.pau@...rix.com>
Subject: Re: [PATCH v1 1/4] xen/acpi: upload power and performance related
 data from a PVH dom0

On 04.12.24 09:24, Penny Zheng wrote:
> From: Roger Pau Monné <roger.pau@...rix.com>
> 
> When running as a PVH dom0 the ACPI MADT is crafted by Xen in order to
> report the correct numbers of vCPUs that dom0 has, so the host MADT is
> not provided to dom0.  This creates issues when parsing the power and
> performance related data from ACPI dynamic tables, as the ACPI
> Processor UIDs found on the dynamic code are likely to not match the
> ones crafted by Xen in the dom0 MADT.
> 
> Xen would rely on Linux having filled at least the power and
> performance related data of the vCPUs on the system, and would clone
> that information in order to setup the remaining pCPUs on the system
> if dom0 vCPUs < pCPUs.  However when running as PVH dom0 it's likely
> that none of dom0 CPUs will have the power and performance data
> filled, and hence the Xen ACPI Processor driver needs to fetch that
> information by itself.
> 
> In order to do so correctly, introduce a new helper to fetch the _CST
> data without taking into account the system capabilities from the
> CPUID output, as the capabilities reported to dom0 in CPUID might be
> different from the ones on the host.
> 
> Note that the newly introduced code will only fetch the _CST, _PSS,
> _PPC and _PCT from a single CPU, and clone that information for all the
> other Processors.  This won't work on an heterogeneous system with
> Processors having different power and performance related data between
> them.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@...rix.com>
> Signed-off-by: Jason Andryuk <jason.andryuk@....com>

I think this is the V2 version of Jason's patch, of which he sent V3 just
yesterday?

Please sync with him how to proceed: is his patch meant to be a prerequisite
for your series or a part of it?


Juergen

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