Re: [patch v11 12/23] ARM64 / ACPI: Parse MADT for SMP initialization

[Hanjun Guo]

On 2015å03æ27æ 05:12, Will Deacon wrote:
> On Thu, Mar 26, 2015 at 07:48:50PM +0000, Hanjun Guo wrote:
> > On 2015å03æ26æ 23:15, Will Deacon wrote:
> > > commit 8ef320319592693f4a6286d80df210fd47b3e356
> > > Author: Will Deacon <will.deacon@xxxxxxx>
> > > Date:   Thu Mar 26 15:09:20 2015 +0000
> > >
> > >       ARM64 / ACPI: fix usage of acpi_map_gic_cpu_interface
> > >
> > >       acpi_parse_gic_cpu_interface calls acpi_map_gic_cpu_interface by both
> > >       passing a 32-bit value in the u8 enabled parameter and then subsequently
> > >       ignoring its return value.
> > >
> > >       Sort it out.
> > >
> > >       Reported-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> > >       Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
> > >
> > > diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> > > index cd60329da8c4..07649e413244 100644
> > > --- a/arch/arm64/kernel/acpi.c
> > > +++ b/arch/arm64/kernel/acpi.c
> > > @@ -103,9 +103,12 @@ void __init __acpi_unmap_table(char *map, unsigned long size)
> > >     *
> > >     * Returns the logical cpu number which maps to MPIDR
> > >     */
> > > -static int __init acpi_map_gic_cpu_interface(u64 mpidr, u8 enabled)
> > > +static int __init
> > > +acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
> >
> > How about just replace u8 with u32? This function has its purpose to
> > be lived, on x86/ia64, ACPI core will get the physcal cpu ID via
> > ACPI handle, then pass it to the arch specific mapping function
> > to map the physcal cpu ID with logical cpu ID for the new added
> > CPU, so when ACPI based CPU hot-plug is introduced on ARM64, we
> > need to go back to that solution.
>
> If/when that happens, we can change things then. Right now, this is a static
> function with one caller. One step at a time, please.
>
> > >    {
> > >    	int i;
> > > +	u64 mpidr = processor->arm_mpidr & MPIDR_HWID_BITMASK;
> > > +	bool enabled = !!(processor->flags & ACPI_MADT_ENABLED);
> > >
> > >    	if (mpidr == INVALID_HWID) {
> > >    		pr_info("Skip MADT cpu entry with invalid MPIDR\n");
> > > @@ -178,11 +181,7 @@ acpi_parse_gic_cpu_interface(struct acpi_subtable_header *header,
> > >    		return -EINVAL;
> > >
> > >    	acpi_table_print_madt_entry(header);
> > > -
> > > -	acpi_map_gic_cpu_interface(processor->arm_mpidr & MPIDR_HWID_BITMASK,
> > > -		processor->flags & ACPI_MADT_ENABLED);
> > > -
> > > -	return 0;
> > > +	return acpi_map_gic_cpu_interface(processor);
> >
> > I don't think we need to return the error value here, in ACPI
> > core, it will stop the MADT scanning once it returned the error
> > value, but actually we can skip some disabled GICC (cpu) entries
> > and find all the enabled ones in MADT, for example,
> >
> > cpu0 entry, with flag enabled
> > cpu1 entry, disabled  - if we return the error value, table scanning
> >                           will stop
> > cpu2 entry, enabled   - and this cpu will be ignored
>
> Then send me a patch making acpi_map_gic_cpu_interface have a void return
> type. Ignoring the return type is usually a good way to introduce subtle
> bugs.

OK, I will, and I will cleanup the comments for this function too.

Need some sleep first...

Thanks
Hanjun
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