Re: [Xen-devel] [PATCH v2 02/27] ARM: GICv3: allocate LPI pending and property table

[André Przywara <andre.przywara@xxxxxxx>]

On 21/03/17 22:57, Stefano Stabellini wrote:
> On Thu, 16 Mar 2017, Andre Przywara wrote:
>> The ARM GICv3 provides a new kind of interrupt called LPIs.
>> The pending bits and the configuration data (priority, enable bits) for
>> those LPIs are stored in tables in normal memory, which software has to
>> provide to the hardware.
>> Allocate the required memory, initialize it and hand it over to each
>> redistributor. The maximum number of LPIs to be used can be adjusted with
>> the command line option "max_lpi_bits", which defaults to a compile time
>> constant exposed in Kconfig.
>>
>> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>

....

>> diff --git a/xen/arch/arm/gic-v3-lpi.c b/xen/arch/arm/gic-v3-lpi.c
>> new file mode 100644
>> index 0000000..4f8414b
>> --- /dev/null
>> +++ b/xen/arch/arm/gic-v3-lpi.c

....

>> +/*
>> + * Tell a redistributor about the (shared) property table, allocating one
>> + * if not already done.
>> + */
>> +static int gicv3_lpi_set_proptable(void __iomem * rdist_base)
>> +{
>> +    uint64_t reg;
>> +
>> +    reg  = GIC_BASER_CACHE_RaWaWb << 
>> GICR_PROPBASER_INNER_CACHEABILITY_SHIFT;
>> +    reg |= GIC_BASER_CACHE_SameAsInner << 
>> GICR_PROPBASER_OUTER_CACHEABILITY_SHIFT;
>> +    reg |= GIC_BASER_InnerShareable << GICR_PROPBASER_SHAREABILITY_SHIFT;
>> +
>> +    /*
>> +     * The property table is shared across all redistributors, so allocate
>> +     * this only once, but return the same value on subsequent calls.
>> +     */
>> +    if ( !lpi_data.lpi_property )
>> +    {
>> +        /* The property table holds one byte per LPI. */
>> +        unsigned int order = get_order_from_bytes(lpi_data.nr_host_lpis);
>> +        void *table = alloc_xenheap_pages(order, 0);
> 
> you investigated the possibility of using _xmalloc to 64K align it?

Yes, _xmalloc gives me the alignment, but AFAICT not the physical
contiguous memory guarantee the table needs. If there are other ways to
satisfy those requirements, I am all ears. Otherwise I'd just add a
comment to motivate this.

Cheers,
Andre.


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