Re: [PATCH v2 3/3] intel_iommu: Bypass barrier wait descriptor

[Yi Liu]

On 2024/7/4 23:12, CLEMENT MATHIEU--DRIF wrote:
> From: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
>
> wait_desc with SW=0,IF=0,FN=1 must not be considered as an
> invalid descriptor as it is used to implement section 7.10 of
> the VT-d spec

After a second thinking. t would be better to move this patch to the
PRI series [1]. Reason as below:

This wait descriptor is used to drain PRQ. While, the guest need not
to drain PRQ until the PRI series which advertises the PRI cap to the
guest. So QEMU won't get such a wait descriptor before that series.

[1] 
https://lore.kernel.org/qemu-devel/713ece39-bc1e-4189-a1d9-f81f9cdbd03b@eviden.com/

> Signed-off-by: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
> ---
>   hw/i386/intel_iommu.c | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index be0cb39b5c..12ea3a9aa0 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -2561,6 +2561,12 @@ static bool vtd_process_wait_desc(IntelIOMMUState *s, 
> VTDInvDesc *inv_desc)
>       } else if (inv_desc->lo & VTD_INV_DESC_WAIT_IF) {
>           /* Interrupt flag */
>           vtd_generate_completion_event(s);
> +    } else if (inv_desc->lo & VTD_INV_DESC_WAIT_FN) {
> +        /*
> +         * SW = 0, IF = 0, FN = 1
> +         * This kind of descriptor is defined in section 7.10 of VT-d
> +         * Nothing to do as we process the events sequentially
> +         */
>       } else {
>           error_report_once("%s: invalid wait desc: hi=%"PRIx64", lo=%"PRIx64
>                             " (unknown type)", __func__, inv_desc->hi,

--
Regards,
Yi Liu