Re: [PATCH] irqchip/gic-v3: Fix the driver probe() fail due to disabled GICC entry

[Shanker Donthineni]

Hi Thanks,

On 12/04/2017 04:28 AM, Marc Zyngier wrote:
> On 03/12/17 23:21, Shanker Donthineni wrote:
>> As per MADT specification, it's perfectly valid firmware can pass
>> MADT table to OS with disabled GICC entries. ARM64-SMP code skips
>> those cpu cores to bring online. However the current GICv3 driver
>> probe bails out in this case on systems where redistributor regions
>> are not in the always-on power domain.
>>
>> This patch does the two things to fix the panic.
>>   - Don't return an error in gic_acpi_match_gicc() for disabled GICC.
>>   - No need to keep GICR region information for disabled GICC.
>>
>> Kernel crash traces:
>>   Kernel panic - not syncing: No interrupt controller found.
>>   CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.13.5 #26
>>   [<ffff000008087770>] dump_backtrace+0x0/0x218
>>   [<ffff0000080879dc>] show_stack+0x14/0x20
>>   [<ffff00000883b078>] dump_stack+0x98/0xb8
>>   [<ffff0000080c5c14>] panic+0x118/0x26c
>>   [<ffff000008b62348>] init_IRQ+0x24/0x2c
>>   [<ffff000008b609fc>] start_kernel+0x230/0x394
>>   [<ffff000008b601e4>] __primary_switched+0x64/0x6c
>>   ---[ end Kernel panic - not syncing: No interrupt controller found.
>>
>> Disabled GICC subtable example:
>>                    Subtable Type : 0B [Generic Interrupt Controller]
>>                           Length : 50
>>                         Reserved : 0000
>>             CPU Interface Number : 0000003D
>>                    Processor UID : 0000003D
>>            Flags (decoded below) : 00000000
>>                Processor Enabled : 0
>>  Performance Interrupt Trig Mode : 0
>>  Virtual GIC Interrupt Trig Mode : 0
>>         Parking Protocol Version : 00000000
>>            Performance Interrupt : 00000017
>>                   Parked Address : 0000000000000000
>>                     Base Address : 0000000000000000
>>         Virtual GIC Base Address : 0000000000000000
>>      Hypervisor GIC Base Address : 0000000000000000
>>            Virtual GIC Interrupt : 00000019
>>       Redistributor Base Address : 0000FFFF88F40000
>>                        ARM MPIDR : 000000000000000D
>>                 Efficiency Class : 00
>>                         Reserved : 000000
>>
>> Signed-off-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>
>> ---
>>  drivers/irqchip/irq-gic-v3.c | 14 +++++++++-----
>>  1 file changed, 9 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
>> index b56c3e2..a30fbac 100644
>> --- a/drivers/irqchip/irq-gic-v3.c
>> +++ b/drivers/irqchip/irq-gic-v3.c
>> @@ -1331,6 +1331,10 @@ static int __init gic_of_init(struct device_node *node, struct device_node *pare
>>  	u32 size = reg == GIC_PIDR2_ARCH_GICv4 ? SZ_64K * 4 : SZ_64K * 2;
>>  	void __iomem *redist_base;
>>  
>> +	/* GICC entry which has !ACPI_MADT_ENABLED is not unusable so skip */
>> +	if (!(gicc->flags & ACPI_MADT_ENABLED))
>> +		return 0;
>> +
>>  	redist_base = ioremap(gicc->gicr_base_address, size);
>>  	if (!redist_base)
>>  		return -ENOMEM;
>> @@ -1374,13 +1378,13 @@ static int __init gic_acpi_match_gicc(struct acpi_subtable_header *header,
>>  				(struct acpi_madt_generic_interrupt *)header;
>>  
>>  	/*
>> -	 * If GICC is enabled and has valid gicr base address, then it means
>> -	 * GICR base is presented via GICC
>> +	 * If GICC is enabled and has not valid gicr base address, then it means
>> +	 * GICR base is not presented via GICC
>>  	 */
>> -	if ((gicc->flags & ACPI_MADT_ENABLED) && gicc->gicr_base_address)
>> -		return 0;
>> +	if ((gicc->flags & ACPI_MADT_ENABLED) && (!gicc->gicr_base_address))
>> +		return -ENODEV;
> 
> This doesn't feel quite right. It would mean that having the ENABLED
> flag cleared and potentially no address would make it valid? It looks to
> me that the original code is "less wrong".
> 
> What am I missing?
>

Original definition of the function gic_acpi_match_gicc().
 {
  if ((gicc->flags & ACPI_MADT_ENABLED) && gicc->gicr_base_address)
    return 0;

  return -ENODEV;
 }

Above code triggers the driver probe fail for the two reasons.
  1) GICC with ACPI_MADT_ENABLED=0, it's a bug according to ACPI spec.
  2) GICC with ACPI_MADT_ENABLED=1 and invalid GICR address, expected.


This patch fix the first failed case and keep the second case intact.
  if ((gicc->flags & ACPI_MADT_ENABLED) && (!gicc->gicr_base_address))
    return -ENODEV;

  return 0;

> Thanks,
> 
> 	M.
> 

-- 
Shanker Donthineni
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.