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Date: Fri, 24 Jan 2014 22:37:28 +0800
From: Hanjun Guo <hanjun.guo@...aro.org>
To: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Catalin Marinas <Catalin.Marinas@....com>,
Will Deacon <Will.Deacon@....com>,
Russell King - ARM Linux <linux@....linux.org.uk>,
"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"grant.likely@...aro.org" <grant.likely@...aro.org>,
Matthew Garrett <mjg59@...f.ucam.org>,
Olof Johansson <olof@...om.net>,
Linus Walleij <linus.walleij@...aro.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Rob Herring <robh@...nel.org>,
Mark Rutland <Mark.Rutland@....com>,
Arnd Bergmann <arnd@...db.de>,
"patches@...aro.org" <patches@...aro.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>
Subject: Re: [PATCH 10/20] ARM64 / ACPI: Enumerate possible/present CPU set
and map logical cpu id to APIC id
Hi Lorenzo,
On 2014年01月22日 23:53, Lorenzo Pieralisi wrote:
> On Fri, Jan 17, 2014 at 12:25:04PM +0000, Hanjun Guo wrote:
>
> [...]
>
>> +/* map logic cpu id to physical GIC id */
>> +extern int arm_cpu_to_apicid[NR_CPUS];
>> +#define cpu_physical_id(cpu) arm_cpu_to_apicid[cpu]
> Sudeep already commented on this, please update it accordingly.
Actually after some careful review of the ACPI code, I can't
update it as MPIDR here.
MPIDR can be the ACPI uid and NOT the GIC id, the mapping
of them are something like this in ACPI driver now:
logic cpu id <---> APIC Id (GIC ID) <---> ACPI uid (MPIDR on ARM)
but not logic cpu id <---> ACPI uid directly, you can refer to
the code of processor_core.c
So here I can only map GIC id to logical cpu id.
>
>> +
>> #else /* !CONFIG_ACPI */
>> #define acpi_disabled 1 /* ACPI sometimes enabled on ARM */
>> #define acpi_noirq 1 /* ACPI sometimes enabled on ARM */
>> diff --git a/drivers/acpi/plat/arm-core.c b/drivers/acpi/plat/arm-core.c
>> index 8ba3e6f..1d9b789 100644
>> --- a/drivers/acpi/plat/arm-core.c
>> +++ b/drivers/acpi/plat/arm-core.c
>> @@ -31,6 +31,7 @@
>> #include <linux/smp.h>
>>
>> #include <asm/pgtable.h>
>> +#include <asm/cputype.h>
>>
>> /*
>> * We never plan to use RSDT on arm/arm64 as its deprecated in spec but this
>> @@ -52,6 +53,13 @@ EXPORT_SYMBOL(acpi_pci_disabled);
>> */
>> static u64 acpi_lapic_addr __initdata;
> Is this variable actually needed ?
Yes, needed for GIC initialization.
>
>>
>> +/* available_cpus here means enabled cpu in MADT */
>> +static int available_cpus;
> Ditto.
>
>> +
>> +/* Map logic cpu id to physical GIC id (physical CPU id). */
>> +int arm_cpu_to_apicid[NR_CPUS] = { [0 ... NR_CPUS-1] = -1 };
>> +static int boot_cpu_apic_id = -1;
> Do we need all these variables ? I think we should reuse cpu_logical_map
> data structures for that, it looks suspiciously familiar.
MPIDR is the different part. if we use MPIDR as GIC id, i think
we can reuse cpu_logical_map, but Sudeep suggested not
use MPIDR as GIC id.
>
>> #define BAD_MADT_ENTRY(entry, end) ( \
>> (!entry) || (unsigned long)entry + sizeof(*entry) > end || \
>> ((struct acpi_subtable_header *)entry)->length < sizeof(*entry))
>> @@ -132,6 +140,55 @@ static int __init acpi_parse_madt(struct acpi_table_header *table)
>> * Please refer to chapter5.2.12.14/15 of ACPI 5.0
>> */
>>
>> +/**
>> + * acpi_register_gic_cpu_interface - register a gic cpu interface and
>> + * generates a logic cpu number
>> + * @id: gic cpu interface id to register
>> + * @enabled: this cpu is enabled or not
>> + *
>> + * Returns the logic cpu number which maps to the gic cpu interface
>> + */
>> +static int acpi_register_gic_cpu_interface(int id, u8 enabled)
>> +{
>> + int cpu;
>> +
>> + if (id >= MAX_GIC_CPU_INTERFACE) {
>> + pr_info(PREFIX "skipped apicid that is too big\n");
>> + return -EINVAL;
>> + }
>> +
>> + total_cpus++;
>> + if (!enabled)
>> + return -EINVAL;
>> +
>> + if (available_cpus >= NR_CPUS) {
>> + pr_warn(PREFIX "NR_CPUS limit of %d reached,"
>> + " Processor %d/0x%x ignored.\n", NR_CPUS, total_cpus, id);
>> + return -EINVAL;
>> + }
> Hmm...what if you are missing the boot CPU ? It is a worthy check.
> Have a look at smp_init_cpus(), it does not bail out on cpu>= NR_CPUS
> because you do want to make sure that the DT contains the boot CPU
> node. Same logic applies.
Thanks, I will review he code you mentioned and find a solution
for ACPI part.
>
>> +
>> + available_cpus++;
>> +
> Is available_cpus != num_possible_cpus() ? It does not look like hence
> available_cpus can go.
No, possible cpus include available cpus and disabled cpus
this is useful for ACPI based CPU hot-plug features.
>
>> + /* allocate a logic cpu id for the new comer */
>> + if (boot_cpu_apic_id == id) {
>> + /*
>> + * boot_cpu_init() already hold bit 0 in cpu_present_mask
>> + * for BSP, no need to allocte again.
>> + */
>> + cpu = 0;
>> + } else {
>> + cpu = cpumask_next_zero(-1, cpu_present_mask);
>> + }
>> +
>> + /* map the logic cpu id to APIC id */
>> + arm_cpu_to_apicid[cpu] = id;
>> +
>> + set_cpu_present(cpu, true);
>> + set_cpu_possible(cpu, true);
> This is getting nasty. Before adding this patch and previous ones we
> need to put in place a method for the kernel to make a definite choice between
> ACPI and DT and stick to that. We can't initialize the logical map twice
> (which will happen if your DT has valid cpu nodes and a chosen node pointing
> to proper ACPI tables) or even having some entries initialized from DT and
> others by ACPI. It is a big fat no-no, please update the series accordingly.
really good catch here :)
so the problem here is that should we use both ACPI and DT in one system?
>
>> +
>> + return cpu;
>> +}
>> +
>> static int __init
>> acpi_parse_gic(struct acpi_subtable_header *header, const unsigned long end)
>> {
>> @@ -144,6 +201,16 @@ acpi_parse_gic(struct acpi_subtable_header *header, const unsigned long end)
>>
>> acpi_table_print_madt_entry(header);
>>
>> + /*
>> + * We need to register disabled CPU as well to permit
>> + * counting disabled CPUs. This allows us to size
>> + * cpus_possible_map more accurately, to permit
>> + * to not preallocating memory for all NR_CPUS
>> + * when we use CPU hotplug.
>> + */
>> + acpi_register_gic_cpu_interface(processor->gic_id,
>> + processor->flags & ACPI_MADT_ENABLED);
>> +
>> return 0;
>> }
>>
>> @@ -186,6 +253,19 @@ static int __init acpi_parse_madt_gic_entries(void)
>> return count;
>> }
>>
>> +#ifdef CONFIG_SMP
>> + if (available_cpus == 0) {
>> + pr_info(PREFIX "Found 0 CPUs; assuming 1\n");
>> + arm_cpu_to_apicid[available_cpus] =
>> + read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
>> + available_cpus = 1; /* We've got at least one of these */
>> + }
> I'd rather check the MADT for at least the boot cpu to present, if it is
> not ACPI tables are horribly buggy and the kernel should barf on that.
>
>> +#endif
>> +
>> + /* Make boot-up look pretty */
>> + pr_info("%d CPUs available, %d CPUs total\n", available_cpus,
>> + total_cpus);
> Ok, now, how can we use the "disabled" CPUs == (total_cpus - available_cpus) ?
For cpus can be hot-added later when system is running.
>
> Are we keeping track of them in the kernel at all ? It does not look
> like, so I wonder whether we need this bit of info. I do not see why it
> is pretty to know that there are disabled, aka unusable CPUs.
>
>> return 0;
>> }
>>
>> @@ -321,6 +401,9 @@ int __init early_acpi_boot_init(void)
>> if (acpi_disabled)
>> return -ENODEV;
>>
>> + /* Get the boot CPU's GIC cpu interface id before MADT parsing */
>> + boot_cpu_apic_id = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
> See Sudeep's comment.
I will rework this part to get the GIC cpu interface id, not the MPIDR here.
Thanks
Hanjun
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