On Tue, Mar 21, 2023 at 02:47:46PM +0100, Rafael J. Wysocki wrote: > On Thu, Mar 16, 2023 at 5:43 PM Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote: > > > > In ACPI systems, the OS can direct power management, as opposed to the > > firmware. This OS-directed Power Management is called OSPM. Part of > > telling the firmware that the OS going to direct power management is > > making ACPI "_PDC" (Processor Driver Capabilities) calls. These _PDC > > methods must be evaluated for every processor object. If these _PDC > > calls are not completed for every processor it can lead to > > inconsistency and later failures in things like the CPU frequency > > driver. > > > > In a Xen system, the dom0 kernel is responsible for system-wide power > > management. The dom0 kernel is in charge of OSPM. However, the > > number of CPUs available to dom0 can be different than the number of > > CPUs physically present on the system. > > > > This leads to a problem: the dom0 kernel needs to evaluate _PDC for > > all the processors, but it can't always see them. > > > > In dom0 kernels, ignore the existing ACPI method for determining if a > > processor is physically present because it might not be accurate. > > Instead, ask the hypervisor for this information. > > > > Fix this by introducing a custom function to use when running as Xen > > dom0 in order to check whether a processor object matches a CPU that's > > online. Such checking is done using the existing information fetched > > by the Xen pCPU subsystem, extending it to also store the ACPI ID. > > > > This ensures that _PDC method gets evaluated for all physically online > > CPUs, regardless of the number of CPUs made available to dom0. > > > > Fixes: 5d554a7bb064 ('ACPI: processor: add internal processor_physically_present()') > > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx> > > --- > > Changes since v3: > > - Protect xen_processor_present() definition with CONFIG_ACPI. > > > > Changes since v2: > > - Extend and use the existing pcpu functionality. > > > > Changes since v1: > > - Reword commit message. > > --- > > arch/x86/include/asm/xen/hypervisor.h | 10 ++++++++++ > > drivers/acpi/processor_pdc.c | 11 +++++++++++ > > drivers/xen/pcpu.c | 21 +++++++++++++++++++++ > > 3 files changed, 42 insertions(+) > > > > diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h > > index 5fc35f889cd1..990a1609677e 100644 > > --- a/arch/x86/include/asm/xen/hypervisor.h > > +++ b/arch/x86/include/asm/xen/hypervisor.h > > @@ -63,4 +63,14 @@ void __init xen_pvh_init(struct boot_params *boot_params); > > void __init mem_map_via_hcall(struct boot_params *boot_params_p); > > #endif > > > > +#if defined(CONFIG_XEN_DOM0) && defined(CONFIG_ACPI) > > +bool __init xen_processor_present(uint32_t acpi_id); > > +#else > > +static inline bool xen_processor_present(uint32_t acpi_id) > > +{ > > + BUG(); > > + return false; > > +} > > +#endif > > + > > #endif /* _ASM_X86_XEN_HYPERVISOR_H */ > > diff --git a/drivers/acpi/processor_pdc.c b/drivers/acpi/processor_pdc.c > > index 8c3f82c9fff3..18fb04523f93 100644 > > --- a/drivers/acpi/processor_pdc.c > > +++ b/drivers/acpi/processor_pdc.c > > @@ -14,6 +14,8 @@ > > #include <linux/acpi.h> > > #include <acpi/processor.h> > > > > +#include <xen/xen.h> > > This along with the definition above is evidently insufficient for > xen_processor_present() to always be defined. See > https://lore.kernel.org/linux-acpi/64198b60.bO+m9o5w+Hd8hcF3%25lkp@xxxxxxxxx/T/#u > for example. > > I'm dropping the patch now, please fix and resend. Hello, Sorry. I've sent a followup fix: https://lore.kernel.org/xen-devel/20230321112522.46806-1-roger.pau@xxxxxxxxxx/T/#u Would you be fine with taking such followup, or would rather prefer for me to send the original fixed patch as v5? Thanks, Roger.