Re: [Xen-devel] [RFC v1 02/15] vt-d: VT-d Posted-Interrupts feature detection

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 25/03/15 12:31, Feng Wu wrote:
> VT-d Posted-Interrupts is an enhancement to CPU side Posted-Interrupt.
> With VT-d Posted-Interrupts enabled, external interrupts from
> direct-assigned devices can be delivered to guests without VMM
> intervention when guest is running in non-root mode.
>
> This patch adds feature detection logic for VT-d posted-interrupt.
>
> Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> ---
>   xen/drivers/passthrough/vtd/iommu.c | 15 +++++++++++++--
>   xen/drivers/passthrough/vtd/iommu.h |  1 +
>   2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/xen/drivers/passthrough/vtd/iommu.c 
> b/xen/drivers/passthrough/vtd/iommu.c
> index 891b9e3..86798a3 100644
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -2030,6 +2030,7 @@ static int init_vtd_hw(void)
>               if ( ioapic_to_iommu(IO_APIC_ID(apic)) == NULL )
>               {
>                   iommu_intremap = 0;
> +                iommu_intpost = 0;
>                   dprintk(XENLOG_ERR VTDPREFIX,
>                       "ioapic_to_iommu: ioapic %#x (id: %#x) is NULL! "
>                       "Will not try to enable Interrupt Remapping.\n",
> @@ -2046,6 +2047,7 @@ static int init_vtd_hw(void)
>               if ( enable_intremap(iommu, 0) != 0 )
>               {
>                   iommu_intremap = 0;
> +                iommu_intpost = 0;
>                   dprintk(XENLOG_WARNING VTDPREFIX,
>                           "Interrupt Remapping not enabled\n");
>   
> @@ -2119,8 +2121,8 @@ int __init intel_vtd_setup(void)
>       }
>   
>       /* We enable the following features only if they are supported by all VT-d
> -     * engines: Snoop Control, DMA passthrough, Queued Invalidation and
> -     * Interrupt Remapping.
> +     * engines: Snoop Control, DMA passthrough, Queued Invalidation, Interrupt
> +     * Remapping, and Posted Interrupt
>        */
>       for_each_drhd_unit ( drhd )
>       {
> @@ -2146,7 +2148,13 @@ int __init intel_vtd_setup(void)
>               iommu_qinval = 0;
>   
>           if ( iommu_intremap && !ecap_intr_remap(iommu->ecap) )
> +        {
>               iommu_intremap = 0;
> +            iommu_intpost = 0;
> +        }
> +
> +        if ( iommu_intpost && !cap_intr_post(iommu->cap))
Missing space inside the outer bracket.

I am wondering whether it might be easier, instead of having 
"iommu_intremap = 0; iommu_intpost = 0" all over the place, to instead 
insist that one must check "iommu_intremap && iommu_intpost".
Out of interest, which platforms have intpost capabilities?

~Andrew

> +            iommu_intpost = 0;
>   
>           if ( !vtd_ept_page_compatible(iommu) )
>               iommu_hap_pt_share = 0;
> @@ -2164,6 +2172,7 @@ int __init intel_vtd_setup(void)
>       if ( !iommu_qinval && iommu_intremap )
>       {
>           iommu_intremap = 0;
> +        iommu_intpost = 0;
>           dprintk(XENLOG_WARNING VTDPREFIX, "Interrupt Remapping disabled "
>               "since Queued Invalidation isn't supported or enabled.\n");
>       }
> @@ -2173,6 +2182,7 @@ int __init intel_vtd_setup(void)
>       P(iommu_passthrough, "Dom0 DMA Passthrough");
>       P(iommu_qinval, "Queued Invalidation");
>       P(iommu_intremap, "Interrupt Remapping");
> +    P(iommu_intpost, "Posted Interrupt");
>       P(iommu_hap_pt_share, "Shared EPT tables");
>   #undef P
>   
> @@ -2192,6 +2202,7 @@ int __init intel_vtd_setup(void)
>       iommu_passthrough = 0;
>       iommu_qinval = 0;
>       iommu_intremap = 0;
> +    iommu_intpost = 0;
>       return ret;
>   }
>   
> diff --git a/xen/drivers/passthrough/vtd/iommu.h b/xen/drivers/passthrough/vtd/iommu.h
> index d6e6520..42047e0 100644
> --- a/xen/drivers/passthrough/vtd/iommu.h
> +++ b/xen/drivers/passthrough/vtd/iommu.h
> @@ -69,6 +69,7 @@
>   /*
>    * Decoding Capability Register
>    */
> +#define cap_intr_post(c)       (((c) >> 59) & 1)
>   #define cap_read_drain(c)      (((c) >> 55) & 1)
>   #define cap_write_drain(c)     (((c) >> 54) & 1)
>   #define cap_max_amask_val(c)   (((c) >> 48) & 0x3f)

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