Re: [Xen-devel] [PATCH v3 60/62] arm/acpi: Configure interrupts dynamically

[Shannon Zhao <zhaoshenglong@xxxxxxxxxx>]

Hi,

On 2015/11/30 23:42, Julien Grall wrote:
> Hi Shannon,
> 
> On 17/11/15 09:40, shannon.zhao@xxxxxxxxxx wrote:
>> From: Parth Dixit <parth.dixit@xxxxxxxxxx>
>>
>> Interrupt information is described in DSDT and is not available at
>> the time of booting. Configure the interrupts dynamically when requested
>> by Dom0
> 
> Missing ".".
> 
> As said on a previous version of this patch [1], I'd like to keep the
> ACPI changes very contained to Xen boot. Your change is not ACPI
> specific and could be used for DT.
> 
>>
>> Signed-off-by: Parth Dixit <parth.dixit@xxxxxxxxxx>
>> Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
>> ---
>>  xen/arch/arm/vgic.c | 19 +++++++++++++++++++
>>  1 file changed, 19 insertions(+)
>>
>> diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
>> index 7bb4570..d05abde 100644
>> --- a/xen/arch/arm/vgic.c
>> +++ b/xen/arch/arm/vgic.c
>> @@ -25,6 +25,7 @@
>>  #include <xen/irq.h>
>>  #include <xen/sched.h>
>>  #include <xen/perfc.h>
>> +#include <xen/acpi.h>
>>  
>>  #include <asm/current.h>
>>  
>> @@ -310,6 +311,8 @@ void vgic_disable_irqs(struct vcpu *v, uint32_t r, int n)
>>      }
>>  }
>>  
>> +#define VGIC_ICFG_MASK(intr) ( 1 << ( ( 2 * ( intr % 16 ) ) + 1 ) )
>> +
>>  void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
>>  {
>>      struct domain *d = v->domain;
>> @@ -321,7 +324,23 @@ void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
>>      struct vcpu *v_target;
>>  
>>      while ( (i = find_next_bit(&mask, 32, i)) < 32 ) {
>> +#ifdef CONFIG_ACPI
>> +        struct vgic_irq_rank *vr = vgic_get_rank(v, n);
>> +        uint32_t tr;
>> +
>>          irq = i + (32 * n);
>> +        if( ( !acpi_disabled ) && ( n != 0 ) && is_hardware_domain(d) )
> 
> You need to add a comment explaining the ( n != 0 ) i.e we don't SGIs
> and PPIs are RO. It's implementation defined for PPI but it's preferable
> to let Xen take care of it.
> 
> Also, we should set the type only for IRQ assigned to DOM0 (i.e p->desc
> != NULL). With your current solution, DOM0 may change the configuration
> of the serial IRQ by mistake and take down Xen because the physical IRQ
> is enabled and the behavior will be unpredictable.
> 
>> +        {
>> +            tr = vr->icfg[i >> 4] ;
>> +
>> +            if( ( tr & VGIC_ICFG_MASK(i) ) )
>> +                irq_set_type(irq, ACPI_IRQ_TYPE_EDGE_BOTH);
>> +            else
>> +                irq_set_type(irq, ACPI_IRQ_TYPE_LEVEL_MASK);
> 
> Given that only SPI can be configured it would have been better to call
> irq_set_type.
> 
> Although, those 2 functions don't do what you think. They are setting
> the type internally in Xen but don't change the GIC interrupt
> configuration register.
> 
Here it wants to set the type according to the value of GIC ICFG.

I don't know this well. Does it need to set the type here when Dom0
configures the interrupts since I have set them as ACPI_IRQ_TYPE_NONE in
patch 55?

How about following way?
1) In patch 55, it only permit the access of Dom0 to those irqs, not set
the type.
2) Then in this function or in the handler of writing GIC ICFG, check if
the irq is permitted and set the irq type.

> Lastly, they will fail because the configuration has been set earlier
> (as you did in patch #55)
> 
>> +        }
>> +#else
>> +        irq = i + (32 * n);
>> +#endif
>>          v_target = d->arch.vgic.handler->get_target_vcpu(v, irq);
>>          p = irq_to_pending(v_target, irq);
>>          set_bit(GIC_IRQ_GUEST_ENABLED, &p->status);
>>
> 
> Regards,
> 
> [1] http://lists.xen.org/archives/html/xen-devel/2015-06/msg01128.html
> 

-- 
Shannon


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