On Mon, Oct 27, 2014 at 09:58:10AM +0000, Hanjun Guo wrote:
[...]
+static int map_gicc_mpidr(struct acpi_subtable_header *entry,
int device_declaration, u32 acpi_id, int *mpidr)+{
- struct acpi_madt_generic_interrupt *gicc =
container_of(entry, struct acpi_madt_generic_interrupt, header);- if (!(gicc->flags & ACPI_MADT_ENABLED))
return -ENODEV;- /* In the GIC interrupt model, logical processors are
* required to have a Processor Device object in the DSDT,* so we should check device_declaration here*/- if (device_declaration && (gicc->uid == acpi_id)) {
/** Only bits [0:7] Aff0, bits [8:15] Aff1, bits [16:23] Aff2* and bits [32:39] Aff3 are meaningful, so pack the Affx* fields into a single 32 bit identifier to accommodate the* acpi processor drivers.*/*mpidr = ((gicc->arm_mpidr & 0xff00000000) >> 8)| gicc->arm_mpidr;The simple fact that you define a function to pack the mpidr value and you can't use it here because this is *generic* code is telling, and a very bad omen. At the cost of sounding like a broken record, I do not like this mpidr->apic->logical_cpu song and dance at all. ACPI is peppered with code (eg hotplug is another example, CPUidle driver even worse) that is supposed to be generic but contains x86 code to carry out this cpuid conversion, I really think that in order to start an ARM64 ACPI port properly we should at least try to factor out this physical to logical cpu id conversion, and it is not the first time that I mention this on the lists.
I know, thanks for pointing this out. As I replied in previous version of this patch set, apic_id is x86/ia64 specific, but the meaning behind it is not. It means the CPU hardware id to identify itself in the system, it just like MPIDR on ARM.
Yes, except that it is called apic_id.
I will send out a patch for RFC to convert apic_id to physid which is generic for all platforms.
That seems a good idea to sound out if I am the only one having an issue with the current approach.
I will also talk to Rafael about this at the earliest opportunity, I guess that x86 code relies on apic-id because some ACPI versions could not rely on the acpi-id or some other reasons I have to investigate.
As ACPI spec (section 8.4, Declaring Processors) said, Each processor in the system must be declared in the ACPI namespace, so each cpu will have acpi_id in all ACPI versions, and in theory we can map acpi_id to logical cpu id if we want to.
But things are complicated, apic_id is connected to many tables, MADT for smp init, DSDT for device driver, and SRAT for NUMA (there is no acpi_id in it, ONLY has apic_id in the table for x86/ia64), so if we want to factor the code to map acpi_id to logical cpu id, we need to modify:
- ACPI drivers;
- SMP init for x86 and ia64
- the mappings for NUMA init for x86 and ia64
that will be lots of work I think.
I'm willing to discuss this further and come out a solution, please comment on what I said and share your ideas :)
Factoring out apic_id to a common cpu_physical_id is ok to me, because basically that's what you are doing except for the naming. I do not have any particular preference for the acpi_id, I mentioned that only as a means to implement a generic cpu_physical_id, arch agnostic.
Drop the RFC you mentioned above please on the list, we will restart debating from there.
Thanks, Lorenzo