Re: [Xen-devel] [PATCH V4 2/8] iommu/arm: Add ability to handle deferred probing request

[Oleksandr <olekstysh@xxxxxxxxx>]

On 19.09.19 12:44, Julien Grall wrote:
> Hi Oleksandr,
Hi, Julien.


> On 13/09/2019 16:35, Oleksandr Tyshchenko wrote:
> > diff --git a/xen/drivers/passthrough/arm/iommu.c 
> > b/xen/drivers/passthrough/arm/iommu.c
> > index f219de9..555acfc 100644
> > --- a/xen/drivers/passthrough/arm/iommu.c
> > +++ b/xen/drivers/passthrough/arm/iommu.c
> > @@ -20,6 +20,12 @@
> >   #include <xen/device_tree.h>
> >   #include <asm/device.h>
> >   +/*
> > + * Deferred probe list is used to keep track of devices for which 
> > driver
> > + * requested deferred probing (returned -EAGAIN).
> > + */
> > +static __initdata LIST_HEAD(deferred_probe_list);
> > +
> >   static const struct iommu_ops *iommu_ops;
> >     const struct iommu_ops *iommu_get_ops(void)
> > @@ -42,7 +48,7 @@ void __init iommu_set_ops(const struct iommu_ops *ops)
> >     int __init iommu_hardware_setup(void)
> >   {
> > -    struct dt_device_node *np;
> > +    struct dt_device_node *np, *tmp;
> >       int rc;
> >       unsigned int num_iommus = 0;
> >   @@ -51,6 +57,21 @@ int __init iommu_hardware_setup(void)
> >           rc = device_init(np, DEVICE_IOMMU, NULL);
> >           if ( !rc )
> >               num_iommus++;
> > +        else if ( rc == -EAGAIN )
> > +        {
> > +            /*
> > +             * We expect nobody uses device's domain_list at such 
> > early stage,
> NIT: s/We expect nobody uses/Nobody should use/
ok


> > +             * so we can re-use it to link the device in the 
> > deferred list to
> > +             * avoid introducing extra list_head field in struct 
> > dt_device_node.
> > +             */
> > +            ASSERT(list_empty(&np->domain_list));
> [...]
>
> >   void __hwdom_init arch_iommu_check_autotranslated_hwdom(struct 
> > domain *d)
> > diff --git a/xen/include/asm-arm/device.h b/xen/include/asm-arm/device.h
> > index 63a0f36..ee1c3bc 100644
> > --- a/xen/include/asm-arm/device.h
> > +++ b/xen/include/asm-arm/device.h
> > @@ -44,7 +44,11 @@ struct device_desc {
> >       enum device_class class;
> >       /* List of devices supported by this driver */
> >       const struct dt_device_match *dt_match;
> > -    /* Device initialization */
> > +    /*
> > +     * Device initialization.
> > +     *
> > +     * -EAGAIN is used to indicate that device probing is deferred.
> > +     */
> >       int (*init)(struct dt_device_node *dev, const void *data);
> >   };
> >   diff --git a/xen/include/xen/device_tree.h 
> > b/xen/include/xen/device_tree.h
> > index 9a7a8f2..3702e9b 100644
> > --- a/xen/include/xen/device_tree.h
> > +++ b/xen/include/xen/device_tree.h
> > @@ -92,6 +92,13 @@ struct dt_device_node {
> >         /* IOMMU specific fields */
> >       bool is_protected;
> > +    /*
> > +     * The main purpose of this list node is to link the structure 
> > in the list
> s/node//?
ok


> > +     * of devices assigned to domain.
> > +     *
> > +     * Boot code (iommu_hardware_setup) re-uses this list to link 
> > the structure
> > +     * in the list of devices for which driver requested deferred 
> > probing.
> > +     */
> >       struct list_head domain_list;
> >         struct device dev;
> With the two above addressed and pending the patch it depends on [1] 
> is acked:
> Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
Thank you.


Can I do anything to speed up [1]? That patch was tested and worked fine.


> Cheers,
>
> [1] 
> https://lists.xenproject.org/archives/html/xen-devel/2019-08/msg01924.html
--
Regards,

Oleksandr Tyshchenko


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