On Wed, 17 Apr 2024 17:59:36 +0200 "Rafael J. Wysocki" <rafael@xxxxxxxxxx> wrote: > On Wed, Apr 17, 2024 at 5:38 PM Jonathan Cameron > <Jonathan.Cameron@xxxxxxxxxx> wrote: > > > > On Wed, 17 Apr 2024 16:03:51 +0100 > > Salil Mehta <salil.mehta@xxxxxxxxxx> wrote: > > > > > > From: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx> > > > > Sent: Wednesday, April 17, 2024 2:19 PM > > > > > > > > From: James Morse <james.morse@xxxxxxx> > > > > > > > > The arm64 specific arch_register_cpu() call may defer CPU registration until > > > > the ACPI interpreter is available and the _STA method can be evaluated. > > > > > > > > If this occurs, then a second attempt is made in acpi_processor_get_info(). > > > > Note that the arm64 specific call has not yet been added so for now this will > > > > be called for the original hotplug case. > > > > > > > > For architectures that do not defer until the ACPI Processor driver loads > > > > (e.g. x86), for initially present CPUs there will already be a CPU device. If > > > > present do not try to register again. > > > > > > > > Systems can still be booted with 'acpi=off', or not include an ACPI > > > > description at all as in these cases arch_register_cpu() will not have > > > > deferred registration when first called. > > > > > > > > This moves the CPU register logic back to a subsys_initcall(), while the > > > > memory nodes will have been registered earlier. > > > > Note this is where the call was prior to the cleanup series so there should be > > > > no side effects of moving it back again for this specific case. > > > > > > > > [PATCH 00/21] Initial cleanups for vCPU HP. > > > > https://lore.kernel.org/all/ZVyz%2FVe5pPu8AWoA@xxxxxxxxxxxxxxxxxxxxx/ > > > > > > > > e.g. 5b95f94c3b9f ("x86/topology: Switch over to GENERIC_CPU_DEVICES") > > > > > > > > Signed-off-by: James Morse <james.morse@xxxxxxx> > > > > Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx> > > > > Tested-by: Miguel Luis <miguel.luis@xxxxxxxxxx> > > > > Tested-by: Vishnu Pajjuri <vishnu@xxxxxxxxxxxxxxxxxxxxxx> > > > > Tested-by: Jianyong Wu <jianyong.wu@xxxxxxx> > > > > Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx> > > > > Co-developed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > > > > Signed-off-by: Joanthan Cameron <Jonathan.Cameron@xxxxxxxxxx> > > > > --- > > > > v6: Squash the two paths for conventional CPU Hotplug and arm64 > > > > vCPU HP. > > > > v5: Update commit message to make it clear this is moving the > > > > init back to where it was until very recently. > > > > > > > > No longer change the condition in the earlier registration point > > > > as that will be handled by the arm64 registration routine > > > > deferring until called again here. > > > > --- > > > > drivers/acpi/acpi_processor.c | 12 +++++++++++- > > > > 1 file changed, 11 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c > > > > index 7ecb13775d7f..0cac77961020 100644 > > > > --- a/drivers/acpi/acpi_processor.c > > > > +++ b/drivers/acpi/acpi_processor.c > > > > @@ -356,8 +356,18 @@ static int acpi_processor_get_info(struct > > > > acpi_device *device) > > > > * > > > > * NOTE: Even if the processor has a cpuid, it may not be present > > > > * because cpuid <-> apicid mapping is persistent now. > > > > + * > > > > + * Note this allows 3 flows, it is up to the arch_register_cpu() > > > > + * call to reject any that are not supported on a given architecture. > > > > + * A) CPU becomes present. > > > > + * B) Previously invalid logical CPU ID (Same as becoming present) > > > > + * C) CPU already present and now being enabled (and wasn't > > > > registered > > > > + * early on an arch that doesn't defer to here) > > > > */ > > > > - if (invalid_logical_cpuid(pr->id) || !cpu_present(pr->id)) { > > > > + if ((!invalid_logical_cpuid(pr->id) && cpu_present(pr->id) && > > > > + !get_cpu_device(pr->id)) || > > > > + invalid_logical_cpuid(pr->id) || > > > > + !cpu_present(pr->id)) { > > > > > > > > Hi Salil, > > > > Thanks for quick review! > > > > > Logic is clear but it is ugly. We should turn them into macro or inline. > > > > You've found the 'ugly' in this approach vs keeping them separate. > > > > For this version I wanted to keep it clear that indeed this condition > > is a complex mess of different things (and to let people compare > > it easily with the two paths in v5 to convinced themselves this > > is the same) > > > > It's also a little tricky to do, so will need some thought. > > > > I don't think a simple acpi_cpu_is_hotplug() condition is useful > > as it just moves the complexity away from where a reader is looking > > and it would only be used in this one case. > > > > It doesn't separate well into finer grained subconditions because > > (C) is a messy case of the vCPU HP case and a not done > > something else earlier. The disadvantage of only deferring for > > arm64 and not other architectures. > > > > The best I can quickly come up with is something like this: > > #define acpi_cpu_not_present(cpu) \ > > (invalid_logical_cpuid(cpu) || !cpu_present(cpu)) > > #define acpi_cpu_not_enabled(cpu) \ > > (!invalid_logical_cpuid(cpu) || cpu_present(cpu)) > > > > if ((apci_cpu_not_enabled(pr->id) && !get_cpu_device(pr->id) || > > acpi_cpu_not_present(pr->id)) > > > > Which would still need the same amount of documentation. The > > code still isn't enough for me to immediately be able to see > > what is going on. > > > > So maybe worth it... I'm not sure. Rafael, you get to keep this > > fun, what would you prefer? > > I would use a static inline function returning bool to carry out these > checks with comments explaining the different cases in which 'true' > needs to be returned. The following makes a subtle logic change (I'll retest tomorrow) but I think that get_cpu_device(cpu) can never succeed in a path where hotadd makes sense. +/* + * Identify if the state transition indicates that hotadd_init + * should be called. + * + * For acpi_processor_add() to be called, the reported state must + * now be enabled and present. Conditions reflect prior state. + */ +static inline bool acpi_processor_should_hotadd_init(int cpu) +{ + /* Already register, initial registration was not deferred */ + if (get_cpu_device(cpu)) + return false; + + /* Processor has become present */ + if (!cpu_present(cpu)) + return true; + + /* Logical cpuid currently invalid indicates hotadd */ + if (invalid_logical_cpuid(cpu)) + return true; + + /* + * Previously present and the logical cpu id is valid. + * Deferred registration now _STA can be queries, or + * Hotadd due to enabled becoming true on an online capable + * CPU. + */ + if (cpu_present(cpu)) + return true; + + return false; +} + static int acpi_processor_get_info(struct acpi_device *device) { union acpi_object object = { 0 }; @@ -356,18 +388,8 @@ static int acpi_processor_get_info(struct acpi_device *device) * * NOTE: Even if the processor has a cpuid, it may not be present * because cpuid <-> apicid mapping is persistent now. - * - * Note this allows 3 flows, it is up to the arch_register_cpu() - * call to reject any that are not supported on a given architecture. - * A) CPU becomes present. - * B) Previously invalid logical CPU ID (Same as becoming present) - * C) CPU already present and now being enabled (and wasn't registered - * early on an arch that doesn't defer to here) */ - if ((!invalid_logical_cpuid(pr->id) && cpu_present(pr->id) && - !get_cpu_device(pr->id)) || - invalid_logical_cpuid(pr->id) || - !cpu_present(pr->id)) { + if (acpi_processor_should_hotadd_init(pr->id)) { ret = acpi_processor_hotadd_init(pr, device);
