Re: [Xen-devel] [PATCH 0/4] ARM: ACPI: ITS: Add ITS Support for ACPI hardware domain

[Julien Grall <julien.grall@xxxxxxx>]

On 10/08/17 12:21, Manish Jaggi wrote:
> Hi Julien,
>
> On 6/21/2017 6:53 PM, Julien Grall wrote:
> > Hi Manish,
> >
> > On 21/06/17 02:01, Manish Jaggi wrote:
> > > This patch series adds the support of ITS for ACPI hardware domain.
> > > It is tested on staging branch with has ITS v12 patchset by Andre.
> > >
> > > I have tried to incorporate the review comments on the RFC v1/v2 patch.
> > > The single patch in RFC is now split into 4 patches.
> > I will comment here rather than on each patches.
> >
> > > Patch1: ARM: ITS: Add translation_id to host_its
> > >  Adds translation_id in host_its data structure, which is populated from
> > >  translation_id read from firmwar MADT. This value is then programmed
> > > into
> > >  local MADT created for hardware domain in patch 4.
> > I don't see any reason to store value that will only be used for
> > generating the MADT which BTW is just a copy for the ITS. Instead we
> > should copy over the MADT entries.
> There are two approaches,
>
> If I use the standard API  acpi_table_parse_madt which would iterate
> over ACPI_MADT_TYPE_GENERIC_TRANSLATOR entries, I have to maintain the
> addr and translation_id in some data structure, to be filled later in
> the hwdomain copy of madt generic translator.
>
> If I don't use the standard API I have to add code to manually parse all
> the translator entries.
There are a 3rd approach I suggested and ignored... The ITS entries for 
Dom0 is exactly the same as the host entries. So you only need to do a 
verbatim copy of the entry...
> Which of the two you find cleaner?
> > This would also avoid to introduce a fake ID for DT as you currently
> > do in patch #2.
> This can be avoided by storing translator_id only for acpi.
>
> +static int add_to_host_its_list(u64 addr, u64 size,
> +                      u32 translation_id, const void *node)
> +{
> +    struct host_its *its_data;
> +    its_data = xzalloc(struct host_its);
> +
> +    if ( !its_data )
> +        return -1;
> +
> +    if ( node )
> +        its_data->dt_node = node;
> +    else
> +        its_data->translation_id = translation_id;
> +
> +    its_data->addr = addr;
> +    its_data->size = size;
> +    printk("GICv3: Found ITS @0x%lx\n", addr);
> +
> +    list_add_tail(&its_data->entry, &host_its_list);
> +
> +    return 0;
>
> What do you think?
I don't want to see the translation_id stored for no use at all but 
creating the DOM0 ACPI tables. Is that clearer?
Cheers,

--
Julien Grall

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