Re: git: 67f2a563bfca - main - acpi: Tell SMM we will handle CPPC notifications

On 10 Oct 2022, at 14:53, Tom Jones <thj@FreeBSD.org> wrote:
> 
> The branch main has been updated by thj:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=67f2a563bfcad75c16536ca500b06ddc9306dfa0
> 
> commit 67f2a563bfcad75c16536ca500b06ddc9306dfa0
> Author:     Tom Jones <thj@FreeBSD.org>
> AuthorDate: 2022-10-10 13:46:25 +0000
> Commit:     Tom Jones <thj@FreeBSD.org>
> CommitDate: 2022-10-10 13:53:15 +0000
> 
>    acpi: Tell SMM we will handle CPPC notifications
> 
>    Buggy SMM implementations can hang while processing CPPC notifications.
>    This leads to some laptops (notably Thinkpads) hanging when the
>    hwpstate_intel driver is loaded.
> 
>    Tell the SMM that we will handle CPPC notifications as described in:
> 
>    - Intel® Processor Vendor-Specific ACPI
>    - Intel® 64 and IA-32 Architectures Software Developer’s Manual
> 
>    CPPC events default to masked (disabled) so while we do not do any
>    handling right now this does not seem to lead to any issues.
> 
>    This approach was found via this Linux Kernel patch:
>    https://lkml.org/lkml/2016/3/17/563
> 
>    PR:             253288
>    Reviewed by:    imp, jhb
>    Sponsored by:   Modirum
>    Sponsored by:   Klara, Inc.
>    Differential Revision:  https://reviews.freebsd.org/D36699
> ---
> sys/dev/acpica/acpi_cpu.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
> 
> diff --git a/sys/dev/acpica/acpi_cpu.c b/sys/dev/acpica/acpi_cpu.c
> index 762ea37cfa34..49d2bd11fdaa 100644
> --- a/sys/dev/acpica/acpi_cpu.c
> +++ b/sys/dev/acpica/acpi_cpu.c
> @@ -153,6 +153,7 @@ static struct sysctl_ctx_list cpu_sysctl_ctx;
> static struct sysctl_oid *cpu_sysctl_tree;
> static int		 cpu_cx_generic;
> static int		 cpu_cx_lowest_lim;
> +static bool		 cppc_notify;
> 
> static struct acpi_cpu_softc **cpu_softc;
> ACPI_SERIAL_DECL(cpu, "ACPI CPU");
> @@ -396,6 +397,13 @@ acpi_cpu_attach(device_t dev)
>      */
>     if (!acpi_disabled("mwait") && cpu_mwait_usable())
> 	sc->cpu_features |= ACPI_CAP_SMP_C1_NATIVE | ACPI_CAP_SMP_C3_NATIVE;
> +
> +    /*
> +     * Work around a lingering SMM bug which leads to freezes when handling
> +     * CPPC notifications. Tell the SMM we will handle any CPPC notifications.
> +     */
> +    if ((cpu_power_eax & CPUTPM1_HWP_NOTIFICATION) && cppc_notify)
> +	    sc->cpu_features |= ACPI_CAP_INTR_CPPC;
> #endif
> 
>     if (devclass_get_drivers(device_get_devclass(dev), &drivers,
> @@ -977,6 +985,12 @@ acpi_cpu_startup(void *arg)
> 	NULL, 0, acpi_cpu_global_cx_lowest_sysctl, "A",
> 	"Global lowest Cx sleep state to use");
> 
> +    /* Add sysctl handler to control registering for CPPC notifications */
> +    cppc_notify = 1;
> +    SYSCTL_ADD_BOOL(&cpu_sysctl_ctx, SYSCTL_CHILDREN(cpu_sysctl_tree),
> +	OID_AUTO, "cppc_notify", CTLFLAG_RDTUN | CTLFLAG_MPSAFE,
> +	&cppc_notify, 0, "Register for CPPC Notifications");
> +

This isn’t under an ifdef?

Jess

>     /* Take over idling from cpu_idle_default(). */
>     cpu_cx_lowest_lim = 0;
>     CPU_FOREACH(i) {