Re: [PATCH v3 05/11] xen/arm: gicv3: implement handling of GICv3.1 eSPI

[Leonid Komarianskyi <Leonid_Komarianskyi@xxxxxxxx>]

Hello Oleksandr,

Thank you for your good question, I was thinking about that as well.

On 27.08.25 13:25, Oleksandr Tyshchenko wrote:
> 
> 
> On 26.08.25 17:05, Leonid Komarianskyi wrote:
> 
> 
> Hello Leonid,
> 
> In general patch looks good to me, just one question below ...
> 
>> Introduced appropriate register definitions, helper macros,
>> and initialization of required GICv3.1 distributor registers
>> to support eSPI. This type of interrupt is handled in the
>> same way as regular SPI interrupts, with the following
>> differences:
>>
>> 1) eSPIs can have up to 1024 interrupts, starting from the
>> beginning of the range, whereas regular SPIs use INTIDs from
>> 32 to 1019, totaling 988 interrupts;
>> 2) eSPIs start at INTID 4096, necessitating additional interrupt
>> index conversion during register operations.
>>
>> In case if appropriate config is disabled, or GIC HW doesn't
>> support eSPI, the existing functionality will remain the same.
>>
>> Signed-off-by: Leonid Komarianskyi <leonid_komarianskyi@xxxxxxxx>
>>
>> ---
>> Changes in V2:
>> - move gic_number_espis function from
>>    [PATCH 08/10] xen/arm: vgic: add resource management for extended SPIs
>>    to use it in the newly introduced gic_is_valid_espi
>> - add gic_is_valid_espi which checks if IRQ number is in supported
>>    by HW eSPI range
>> - update gic_is_valid_irq conditions to allow operations with eSPIs
>>
>> Changes in V3:
>> - add __init attribute to gicv3_dist_espi_common_init
>> - change open-codded eSPI register initialization to the appropriate
>>    gen-mask macro
>> - fixed formatting for lines with more than 80 symbols
>> - introduced gicv3_dist_espi_init_aff to be able to use stubs in case of
>>    CONFIG_GICV3_ESPI disabled
>> - renamed parameter in the GICD_TYPER_ESPI_RANGE macro to espi_range
>>    (name was taken from GIC specification) to avoid confusion
>> - changed type for i variable to unsigned int since it cannot be
>>    negative
>> ---
>>   xen/arch/arm/gic-v3.c                  | 80 ++++++++++++++++++++++++++
>>   xen/arch/arm/include/asm/gic.h         | 21 +++++++
>>   xen/arch/arm/include/asm/gic_v3_defs.h | 34 +++++++++++
>>   3 files changed, 135 insertions(+)
>>
>> diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
>> index a959fefebe..3aa5cc1765 100644
>> --- a/xen/arch/arm/gic-v3.c
>> +++ b/xen/arch/arm/gic-v3.c
>> @@ -485,6 +485,36 @@ static void __iomem *get_addr_by_offset(struct 
>> irq_desc *irqd, u32 offset)
>>           default:
>>               break;
>>           }
>> +#ifdef CONFIG_GICV3_ESPI
>> +    case ESPI_BASE_INTID ... ESPI_MAX_INTID:
>> +    {
>> +        u32 irq_index = ESPI_INTID2IDX(irqd->irq);
>> +
>> +        switch ( offset )
>> +        {
>> +        case GICD_ISENABLER:
>> +            return (GICD + GICD_ISENABLERnE + (irq_index / 32) * 4);
>> +        case GICD_ICENABLER:
>> +            return (GICD + GICD_ICENABLERnE + (irq_index / 32) * 4);
>> +        case GICD_ISPENDR:
>> +            return (GICD + GICD_ISPENDRnE + (irq_index / 32) * 4);
>> +        case GICD_ICPENDR:
>> +            return (GICD + GICD_ICPENDRnE + (irq_index / 32) * 4);
>> +        case GICD_ISACTIVER:
>> +            return (GICD + GICD_ISACTIVERnE + (irq_index / 32) * 4);
>> +        case GICD_ICACTIVER:
>> +            return (GICD + GICD_ICACTIVERnE + (irq_index / 32) * 4);
>> +        case GICD_ICFGR:
>> +            return (GICD + GICD_ICFGRnE + (irq_index / 16) * 4);
>> +        case GICD_IROUTER:
>> +            return (GICD + GICD_IROUTERnE + irq_index * 8);
>> +        case GICD_IPRIORITYR:
>> +            return (GICD + GICD_IPRIORITYRnE + irq_index);
>> +        default:
>> +            break;
>> +        }
>> +    }
>> +#endif
>>       default:
>>           break;
>>       }
>> @@ -655,6 +685,52 @@ static void gicv3_set_irq_priority(struct 
>> irq_desc *desc,
>>       spin_unlock(&gicv3.lock);
>>   }
>> +#ifdef CONFIG_GICV3_ESPI
>> +unsigned int gic_number_espis(void)
>> +{
>> +    return gic_hw_ops->info->nr_espi;
>> +}
>> +
>> +static void __init gicv3_dist_espi_common_init(uint32_t type)
>> +{
>> +    unsigned int espi_nr, i;
>> +
>> +    espi_nr = min(1024U, GICD_TYPER_ESPIS_NUM(type));
>> +    gicv3_info.nr_espi = espi_nr;
>> +    /* The GIC HW doesn't support eSPI, so we can leave from here */
>> +    if ( gicv3_info.nr_espi == 0 )
>> +        return;
>> +
>> +    for ( i = 0; i < espi_nr; i += 16 )
>> +        writel_relaxed(0, GICD + GICD_ICFGRnE + (i / 16) * 4);
>> +
>> +    for ( i = 0; i < espi_nr; i += 4 )
>> +        writel_relaxed(GIC_PRI_IRQ_ALL,
>> +                       GICD + GICD_IPRIORITYRnE + (i / 4) * 4);
>> +
>> +    for ( i = 0; i < espi_nr; i += 32 )
>> +    {
>> +        writel_relaxed(GENMASK(31, 0), GICD + GICD_ICENABLERnE + (i / 
>> 32) * 4);
>> +        writel_relaxed(GENMASK(31, 0), GICD + GICD_ICACTIVERnE + (i / 
>> 32) * 4);
>> +    }
>> +
>> +    for ( i = 0; i < espi_nr; i += 32 )
>> +        writel_relaxed(GENMASK(31, 0), GICD + GICD_IGROUPRnE + (i / 
>> 32) * 4);
>> +}
>> +
>> +static void __init gicv3_dist_espi_init_aff(uint64_t affinity)
>> +{
>> +    unsigned int i;
>> +
>> +    for ( i = 0; i < gicv3_info.nr_espi; i++ )
>> +        writeq_relaxed_non_atomic(affinity, GICD + GICD_IROUTERnE + i 
>> * 8);
>> +}
>> +#else
>> +static void __init gicv3_dist_espi_common_init(uint32_t type) { }
>> +
>> +static void __init gicv3_dist_espi_init_aff(uint64_t affinity) { }
>> +#endif
>> +
>>   static void __init gicv3_dist_init(void)
>>   {
>>       uint32_t type;
>> @@ -700,6 +776,8 @@ static void __init gicv3_dist_init(void)
>>       for ( i = NR_GIC_LOCAL_IRQS; i < nr_lines; i += 32 )
>>           writel_relaxed(GENMASK(31, 0), GICD + GICD_IGROUPR + (i / 
>> 32) * 4);
> 
> 
> There is a banner in this function (not visible from the patch context), 
> that prints nr_lines, etc.
> 
> E.g.:
> (XEN) GICv3: 288 lines, (IID 0000043b).
> 
> What do you think, would it be important/valuable to also print nr_espi 
> if non-zero (extended SPI range is supported)?
> 
> 

I think so, it will be useful. By the way, native Linux prints this 
information, so I would prefer to add a message right after checking if 
the hardware supports eSPI:
     /* The GIC HW doesn't support eSPI, so we can leave from here */
     if ( gicv3_info.nr_espi == 0 )
         return;

     printk("GICv3: %d eSPI lines\n", gicv3_info.nr_espi);

This log will appear right after the common one and will look like this:
(XEN) GICv3: 988 lines, (IID 0000043b)
(XEN) GICv3: 1024 eSPI lines

>> +    gicv3_dist_espi_common_init(type);
>> +
>>       gicv3_dist_wait_for_rwp();
>>       /* Turn on the distributor *
>> @@ -713,6 +791,8 @@ static void __init gicv3_dist_init(void)
>>       for ( i = NR_GIC_LOCAL_IRQS; i < nr_lines; i++ )
>>           writeq_relaxed_non_atomic(affinity, GICD + GICD_IROUTER + i 
>> * 8);
>> +
>> +    gicv3_dist_espi_init_aff(affinity);
>>   }
>>
> 
> 
> [snip]
> 
> 
> 

Best regards,
Leonid.