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Message-ID: <20140122155331.GD24288@e102568-lin.cambridge.arm.com>
Date: Wed, 22 Jan 2014 15:53:31 +0000
From: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To: Hanjun Guo <hanjun.guo@...aro.org>
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
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.
> +
> #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 ?
>
> +/* 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.
> #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.
> +
> + available_cpus++;
> +
Is available_cpus != num_possible_cpus() ? It does not look like hence
available_cpus can go.
> + /* 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.
> +
> + 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) ?
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.
Thanks,
Lorenzo
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