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    SubjectRe: [PATCH v8 14/21] ACPI / processor: Make it possible to get CPU hardware ID via GICC
    On 2015年02月04日 04:09, Catalin Marinas wrote:
    > On Tue, Feb 03, 2015 at 02:17:49PM +0000, Mark Rutland wrote:
    >> On Mon, Feb 02, 2015 at 12:45:42PM +0000, Hanjun Guo wrote:
    >>> Introduce a new function map_gicc_mpidr() to allow MPIDRs to be obtained
    >>> from the GICC Structure introduced by ACPI 5.1.
    >>>
    >>> MPIDR is the CPU hardware ID as local APIC ID on x86 platform, so we use
    >>> MPIDR not the GIC CPU interface ID to identify CPUs.
    >>>
    >>> Further steps would typedef a phys_id_t for in arch code(with
    >>> appropriate size and a corresponding invalid value, say ~0) and use that
    >>> instead of an int in drivers/acpi/processor_core.c to store phys_id, then
    >>> no need for mpidr packing.
    >>
    >> I don't understand why we don't fix this now, and I'm very worried that
    >> this patch leaves much potential for FW bugs due to potential Linux
    >> bugs.
    >>
    >> Having a function called cpu_physical_id which _does not_ return a
    >> physical ID makes no sense to me. Any time we really need a physical
    >> ID, we're still going to have to unpack it (in an architecture-specific
    >> manner).
    >
    > Do you mean something like this? Only briefly tested on Juno and I may
    > have missed other calls:

    Thanks, I think it is Mark's suggestion (and also Lorenzo's)

    >
    > diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
    > index ea4d2b35c57b..4fafd62b1b86 100644
    > --- a/arch/arm64/include/asm/acpi.h
    > +++ b/arch/arm64/include/asm/acpi.h
    > @@ -49,33 +49,12 @@ static inline void enable_acpi(void)
    > acpi_noirq = 0;
    > }
    >
    > -/* MPIDR value provided in GICC structure is 64 bits, but the
    > - * existing phys_id (CPU hardware ID) using in acpi processor
    > - * driver is 32-bit, to conform to the same datatype we need
    > - * to repack the GICC structure MPIDR.
    > - *
    > - * bits other than following 32 bits are defined as 0, so it
    > - * will be no information lost after repacked.
    > - *
    > - * Bits [0:7] Aff0;
    > - * Bits [8:15] Aff1;
    > - * Bits [16:23] Aff2;
    > - * Bits [32:39] Aff3;
    > - */
    > -static inline u32 pack_mpidr(u64 mpidr)
    > -{
    > - return (u32) ((mpidr & 0xff00000000) >> 8) | mpidr;
    > -}
    > -
    > /*
    > * The ACPI processor driver for ACPI core code needs this macro
    > * to find out this cpu was already mapped (mapping from CPU hardware
    > * ID to CPU logical ID) or not.
    > - *
    > - * cpu_logical_map(cpu) is the mapping of MPIDR and the logical cpu,
    > - * and MPIDR is the cpu hardware ID we needed to pack.
    > */
    > -#define cpu_physical_id(cpu) pack_mpidr(cpu_logical_map(cpu))
    > +#define cpu_physical_id(cpu) cpu_logical_map(cpu)
    >
    > /*
    > * It's used from ACPI core in kdump to boot UP system with SMP kernel,
    > diff --git a/arch/arm64/include/asm/smp_plat.h b/arch/arm64/include/asm/smp_plat.h
    > index 59e282311b58..a492276e008d 100644
    > --- a/arch/arm64/include/asm/smp_plat.h
    > +++ b/arch/arm64/include/asm/smp_plat.h
    > @@ -40,4 +40,6 @@ static inline u32 mpidr_hash_size(void)
    > extern u64 __cpu_logical_map[NR_CPUS];
    > #define cpu_logical_map(cpu) __cpu_logical_map[cpu]
    >
    > +typedef u64 cpuid_t;

    I think cpuid_t is a little confused because people may recognize
    it as cpu logical id, its original meaning is the physical cpu ID,
    so how about:

    typedef u64 phys_id_t; ?

    Thanks
    Hanjun


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