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Date: Mon, 7 Nov 2016 18:35:49 -0500
From: Peter Xu <peterx@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH V3 05/10] intel_iommu: support device iotlb
 descriptor
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To: Jason Wang <jasowang@redhat.com>
Cc: qemu-devel@nongnu.org, mst@redhat.com, pbonzini@redhat.com, cornelia.huck@de.ibm.com, wexu@redhat.com, vkaplans@redhat.com, Richard Henderson <rth@twiddle.net>, Eduardo Habkost <ehabkost@redhat.com>

On Mon, Nov 07, 2016 at 03:09:50PM +0800, Jason Wang wrote:

[...]

> +static bool vtd_process_device_iotlb_desc(IntelIOMMUState *s,
> +                                          VTDInvDesc *inv_desc)
> +{
> +    VTDAddressSpace *vtd_dev_as;
> +    IOMMUTLBEntry entry;

Since "entry" is allocated on the stack...

[...]

> +    entry.target_as = &vtd_dev_as->as;
> +    entry.addr_mask = sz - 1;
> +    entry.iova = addr;
> +    memory_region_notify_iommu(entry.target_as->root, entry);

... here we need to assign entry.perm explicitly to IOMMU_NONE, right?

Also I think it'll be nice that we set all the fields even not used,
to avoid rubbish from the stack passed down to notifier handlers.

[...]

> +static bool x86_iommu_device_iotlb_prop_get(Object *o, Error **errp)
> +{
> +    X86IOMMUState *s = X86_IOMMU_DEVICE(o);
> +    return s->dt_supported;
> +}
> +
> +static void x86_iommu_device_iotlb_prop_set(Object *o, bool value, Error **errp)
> +{
> +    X86IOMMUState *s = X86_IOMMU_DEVICE(o);
> +    s->dt_supported = value;
> +}
> +
>  static void x86_iommu_instance_init(Object *o)
>  {
>      X86IOMMUState *s = X86_IOMMU_DEVICE(o);
> @@ -114,6 +126,11 @@ static void x86_iommu_instance_init(Object *o)
>      s->intr_supported = false;
>      object_property_add_bool(o, "intremap", x86_iommu_intremap_prop_get,
>                               x86_iommu_intremap_prop_set, NULL);
> +    s->dt_supported = false;
> +    object_property_add_bool(o, "device-iotlb",
> +                             x86_iommu_device_iotlb_prop_get,
> +                             x86_iommu_device_iotlb_prop_set,
> +                             NULL);

Again, a nit-pick here is to use Property for "device-iotlb":

    static Property vtd_properties[] = {
        DEFINE_PROP_UINT32("device-iotlb", X86IOMMUState, dt_supported, false),
        DEFINE_PROP_END_OF_LIST(),
    };

However not worth a repost.

Thanks,

-- peterx