[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <52a2b2f3-ecdc-45fa-afcf-c4d6e2b1dd0c@suse.com>
Date: Wed, 25 Sep 2024 11:17:23 +0200
From: Jürgen Groß <jgross@...e.com>
To: Jason Andryuk <jason.andryuk@....com>,
Stefano Stabellini <sstabellini@...nel.org>,
Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Cc: Roger Pau Monne <roger.pau@...rix.com>, xen-devel@...ts.xenproject.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] xen/acpi: upload power and performance related data
from a PVH dom0
On 16.09.24 22:50, Jason Andryuk wrote:
> From: Roger Pau Monne <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>
> ---
> v2:
> Add second buffer for _CST. Call was failing with
> AE_BUFFER_OVERFLOW(0x000b)
>
> Running a PVH Dom0 on AMD, I needed this v2 change to get the C-State
> information uploaded.
>
> ---
> drivers/xen/pcpu.c | 3 +-
> drivers/xen/xen-acpi-processor.c | 230 ++++++++++++++++++++++++++++---
> include/xen/xen.h | 2 +-
> 3 files changed, 216 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/xen/pcpu.c b/drivers/xen/pcpu.c
> index c63f317e3df3..dc9f2c14bf62 100644
> --- a/drivers/xen/pcpu.c
> +++ b/drivers/xen/pcpu.c
...
> @@ -354,24 +511,44 @@ read_acpi_id(acpi_handle handle, u32 lvl, void *context, void **rv)
> default:
> return AE_OK;
> }
> - if (invalid_phys_cpuid(acpi_get_phys_id(handle,
> - acpi_type == ACPI_TYPE_DEVICE,
> - acpi_id))) {
> +
> + if (!xen_processor_present(acpi_id)) {
> pr_debug("CPU with ACPI ID %u is unavailable\n", acpi_id);
> return AE_OK;
> }
> - /* There are more ACPI Processor objects than in x2APIC or MADT.
> - * This can happen with incorrect ACPI SSDT declerations. */
> - if (acpi_id >= nr_acpi_bits) {
> - pr_debug("max acpi id %u, trying to set %u\n",
> - nr_acpi_bits - 1, acpi_id);
> - return AE_OK;
> - }
> +
> /* OK, There is a ACPI Processor object */
> __set_bit(acpi_id, acpi_id_present);
>
> pr_debug("ACPI CPU%u w/ PBLK:0x%lx\n", acpi_id, (unsigned long)pblk);
>
> + if (!pr_initialized) {
> + struct acpi_processor *pr = context;
> + int rc;
> +
> + /*
> + * There's no CPU on the system that has any performance or
> + * power related data, initialize all the required fields by
> + * fetching that info here.
> + *
> + * Note such information is only fetched once, and then reused
> + * for all pCPUs. This won't work on heterogeneous systems
> + * with different Cx anb/or Px states between CPUs.
> + */
> +
> + pr->handle = handle;
> +
> + rc = acpi_processor_get_performance_info(pr);
> + if (rc)
> + pr_debug("ACPI CPU%u failed to get performance data\n",
> + acpi_id);
Is it really normal to get a failure here? Shouldn't the reaction
be a little bit more visible in this case?
And can you just continue processing?
> + rc = xen_acpi_processor_evaluate_cst(handle, &pr->power);
> + if (rc)
> + pr_debug("ACPI CPU%u failed to get _CST data\n", acpi_id);
Same again. Is pr_debug() enough?
Juergen
Download attachment "OpenPGP_0xB0DE9DD628BF132F.asc" of type "application/pgp-keys" (3684 bytes)
Download attachment "OpenPGP_signature.asc" of type "application/pgp-signature" (496 bytes)
Powered by blists - more mailing lists