Re: [Xen-devel] [PATCH v5 3/7] VT-d: Reduce spin timeout to 1ms, which can be boot-time changed.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.02.16 at 11:18, <quan.xu@xxxxxxxxx> wrote:
> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -968,6 +968,13 @@ Use this to work around firmware issues providing 
> correct RMRR entries. Rather
>  than only mapping RAM pages for IOMMU accesses for Dom0, with this option all
>  pages not marked as unusable in the E820 table will get a mapping 
> established.
>  
> +### vtd\_qi\_timeout (VT-d)
> +> `= <integer>`
> +
> +> Default: `1`
> +
> +>> Specify the timeout of the VT-d Queued Invalidation in ms.
> +
>  ### irq\_ratelimit
>  > `= <integer>`

Just like for patch 2: I'm sure it was mentioned to you before
that this file has its entries (at least mostly) alphabetically sorted.

> @@ -167,10 +172,12 @@ static int queue_invalidate_wait(struct iommu *iommu,
>          start_time = NOW();
>          while ( poll_slot != QINVAL_STAT_DONE )
>          {
> -            if ( NOW() > (start_time + DMAR_OPERATION_TIMEOUT) )
> +            if ( NOW() > (start_time + IOMMU_QI_TIMEOUT) )
>              {
>                  print_qi_regs(iommu);
> -                panic("queue invalidate wait descriptor was not executed");
> +                dprintk(XENLOG_WARNING VTDPREFIX,
> +                        "Queue invalidate wait descriptor was timeout.\n");
> +                return -ETIMEDOUT;
>              }
>              cpu_relax();
>          }

Without a __must_check annotation on the function I cannot see
how I should reasonably convince myself that all call sites now
handle such an error in one way or another.

Jan


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