Re: [Xen-devel] [PATCH 1/2 v5] iommu/amd: Fix logic for clearing the IOMMU interrupt bits

[Suravee Suthikulanit <suravee.suthikulpanit@xxxxxxx>]

On 6/11/2013 1:47 AM, Jan Beulich wrote:
> @@ -611,22 +608,33 @@ static void iommu_check_event_log(struct
>       u32 entry;
>       unsigned long flags;
>   
> +    /* RW1C interrupt status bit */
> +    writel(IOMMU_STATUS_EVENT_LOG_INT_MASK,
> +           iommu->mmio_base + IOMMU_STATUS_MMIO_OFFSET);
> +
>       iommu_read_log(iommu, &iommu->event_log,
>                      sizeof(event_entry_t), parse_event_log_entry);
>   
>       spin_lock_irqsave(&iommu->lock, flags);
>       
> -    /*check event overflow */
> +    /* Check event overflow. */
>       entry = readl(iommu->mmio_base + IOMMU_STATUS_MMIO_OFFSET);
> -
>       if ( iommu_get_bit(entry, IOMMU_STATUS_EVENT_OVERFLOW_SHIFT) )
>           iommu_reset_log(iommu, &iommu->event_log, 
> set_iommu_event_log_control);
> -
> -    /* reset interrupt status bit */
> -    entry = readl(iommu->mmio_base + IOMMU_STATUS_MMIO_OFFSET);
> -    iommu_set_bit(&entry, IOMMU_STATUS_EVENT_LOG_INT_SHIFT);
> -
> -    writel(entry, iommu->mmio_base + IOMMU_STATUS_MMIO_OFFSET);
> +    else
> +    {
> +        entry = readl(iommu->mmio_base + IOMMU_CONTROL_MMIO_OFFSET);
> +        if ( !(entry & IOMMU_CONTROL_EVENT_LOG_INT_MASK) )
> +        {
> +            entry |= IOMMU_CONTROL_EVENT_LOG_INT_MASK;
> +            writel(entry, iommu->mmio_base + IOMMU_CONTROL_MMIO_OFFSET);
> +            /*
> +             * Re-schedule the tasklet to handle eventual log entries added
> +             * between reading the log above and re-enabling the interrupt.
> +             */
> +            tasklet_schedule(&amd_iommu_irq_tasklet);
> +        }
> +    }
If more entries are added to the event log during the time that event 
log interrupt is disabled (in the control register),
the IOMMU hardware will generate interrupt once the the interrupt enable 
bit in the control register changes from 0 to 1 and set the status 
register.  Since the "iommu_interrupt_handler" code is already calling 
"schedule_tasklet",  we should not need to "re-schedule" tasklet here.  
I have confirmed the hardware behavior described with the hardware 
designer.  This is also the same on the PPR log.
Suravee


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