linux-kernel - Re: [PATCH v2] ACPI: Fix initial QoS constraint application order in PPC initialization

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAJZ5v0gf5wb1cNS0CJm9-vhMF63d2BzTEfBciiO9ZhdJHYpDnQ@mail.gmail.com>
Date: Mon, 21 Jul 2025 15:27:09 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Jiayi Li <lijiayi@...inos.cn>
Cc: rafael@...nel.org, jiayi_dec@....com, lenb@...nel.org, 
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ACPI: Fix initial QoS constraint application order in
 PPC initialization

On Mon, Jul 21, 2025 at 5:26 AM Jiayi Li <lijiayi@...inos.cn> wrote:
>
> This patch fixes an issue where _PPC frequency limits set by the BIOS
> failed to take effect due to incorrect call ordering. Previously,
> freq_qos_update_request() was being called before freq_qos_add_request(),
> causing the constraint updates to be ignored. With this fix, the frequency
> limits are now properly enforced as intended.
> The original initialization sequence was:
>
> cpufreq_policy_online()
>     acpi_cpufreq_cpu_init()
>         acpi_processor_get_platform_limit()
>             freq_qos_update_request(&perflib_req)
>     blocking_notifier_call_chain(...)
>         acpi_processor_ppc_init()
>             freq_qos_add_request(&perflib_req)
>
> The new sequence explicitly ensures:
>
> cpufreq_policy_online()
>     acpi_cpufreq_cpu_init()
>         acpi_processor_get_platform_limit()
>             freq_qos_update_request(&perflib_req)
>     blocking_notifier_call_chain(...)
>         acpi_processor_ppc_init()
>             freq_qos_add_request(&perflib_req)
> +           acpi_processor_get_platform_limit()
> +               freq_qos_update_request(&perflib_req)
>
> The critical change adds an immediate platform limit update after the
> QoS request is registered. This guarantees that the initial P-state
> constraint is applied before any subsequent updates, resolving the window
> where constraints could be applied out-of-order.
>
> Fixes: d15ce412737a ("ACPI: cpufreq: Switch to QoS requests instead of cpufreq notifier")
> Signed-off-by: Jiayi Li <lijiayi@...inos.cn>
> ---
> v1 -> v2:
> - Modify the commit.
> - Add pr->performance check in acpi_processor_ppc_init loop.
> ---
> ---
>  drivers/acpi/processor_perflib.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
> index 64b8d1e19594..56f2b8354d62 100644
> --- a/drivers/acpi/processor_perflib.c
> +++ b/drivers/acpi/processor_perflib.c
> @@ -173,6 +173,9 @@ void acpi_processor_ppc_init(struct cpufreq_policy *policy)
>  {
>         unsigned int cpu;
>
> +       if (ignore_ppc == 1)
> +               return;
> +
>         for_each_cpu(cpu, policy->related_cpus) {
>                 struct acpi_processor *pr = per_cpu(processors, cpu);
>                 int ret;
> @@ -180,6 +183,9 @@ void acpi_processor_ppc_init(struct cpufreq_policy *policy)
>                 if (!pr)
>                         continue;
>
> +               if (!pr->performance)
> +                       continue;
> +
>                 /*
>                  * Reset performance_platform_limit in case there is a stale
>                  * value in it, so as to make it match the "no limit" QoS value

Applied, but I have consolidated the pr and pr->performance checks above.

I have also made some changes in the subject and changelog.

Thanks!

> @@ -193,6 +199,11 @@ void acpi_processor_ppc_init(struct cpufreq_policy *policy)
>                 if (ret < 0)
>                         pr_err("Failed to add freq constraint for CPU%d (%d)\n",
>                                cpu, ret);
> +
> +               ret = acpi_processor_get_platform_limit(pr);
> +               if (ret)
> +                       pr_err("Failed to update freq constraint for CPU%d (%d)\n",
> +                              cpu, ret);
>         }
>  }
>
> --