Re: [Xen-devel] [PATCH v7 4/6] VT-d: No need to set irq affinity for posted format IRTE

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.11.16 at 09:10, <feng.wu@xxxxxxxxx> wrote:
> --- a/xen/drivers/passthrough/vtd/intremap.c
> +++ b/xen/drivers/passthrough/vtd/intremap.c
> @@ -597,31 +597,34 @@ static int msi_msg_to_remap_entry(
>  
>      memcpy(&new_ire, iremap_entry, sizeof(struct iremap_entry));
>  
> -    /* Set interrupt remapping table entry */
> -    new_ire.remap.fpd = 0;
> -    new_ire.remap.dm = (msg->address_lo >> MSI_ADDR_DESTMODE_SHIFT) & 0x1;
> -    new_ire.remap.tm = (msg->data >> MSI_DATA_TRIGGER_SHIFT) & 0x1;
> -    new_ire.remap.dlm = (msg->data >> MSI_DATA_DELIVERY_MODE_SHIFT) & 0x1;
> -    /* Hardware require RH = 1 for LPR delivery mode */
> -    new_ire.remap.rh = (new_ire.remap.dlm == dest_LowestPrio);
> -    new_ire.remap.avail = 0;
> -    new_ire.remap.res_1 = 0;
> -    new_ire.remap.vector = (msg->data >> MSI_DATA_VECTOR_SHIFT) &
> -                            MSI_DATA_VECTOR_MASK;
> -    new_ire.remap.res_2 = 0;
> -    if ( x2apic_enabled )
> -        new_ire.remap.dst = msg->dest32;
> -    else
> -        new_ire.remap.dst = ((msg->address_lo >> MSI_ADDR_DEST_ID_SHIFT)
> -                             & 0xff) << 8;
> -
>      if ( pdev )
>          set_msi_source_id(pdev, &new_ire);
>      else
>          set_hpet_source_id(msi_desc->hpet_id, &new_ire);
> -    new_ire.remap.res_3 = 0;
> -    new_ire.remap.res_4 = 0;
> -    new_ire.remap.p = 1;    /* finally, set present bit */
> +
> +    if ( !new_ire.remap.p || !new_ire.remap.im )
> +    {
> +        /* Set interrupt remapping table entry */
> +        new_ire.remap.fpd = 0;
> +        new_ire.remap.dm = (msg->address_lo >> MSI_ADDR_DESTMODE_SHIFT) & 
> 0x1;
> +        new_ire.remap.tm = (msg->data >> MSI_DATA_TRIGGER_SHIFT) & 0x1;
> +        new_ire.remap.dlm = (msg->data >> MSI_DATA_DELIVERY_MODE_SHIFT) & 
> 0x1;
> +        /* Hardware require RH = 1 for LPR delivery mode */
> +        new_ire.remap.rh = (new_ire.remap.dlm == dest_LowestPrio);
> +        new_ire.remap.avail = 0;
> +        new_ire.remap.res_1 = 0;
> +        new_ire.remap.vector = (msg->data >> MSI_DATA_VECTOR_SHIFT) &
> +                                MSI_DATA_VECTOR_MASK;
> +        new_ire.remap.res_2 = 0;
> +        if ( x2apic_enabled )
> +            new_ire.remap.dst = msg->dest32;
> +        else
> +            new_ire.remap.dst = ((msg->address_lo >> MSI_ADDR_DEST_ID_SHIFT)
> +                                 & 0xff) << 8;
> +        new_ire.remap.res_3 = 0;
> +        new_ire.remap.res_4 = 0;
> +        new_ire.remap.p = 1;    /* finally, set present bit */
> +    }

Why does setting the fields depend on the previous state of p and
im? And where's the else to deal with the posted format case? I have
to admit that I don't see how this fits the model previously outlined,
so if you could please explain ...

Jan


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