Re: [Xen-devel] [RFC v2 07/15] vt-d: Add API to update IRTE when VT-d PI is used

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.06.15 at 11:40, <feng.wu@xxxxxxxxx> wrote:
>> -----Original Message-----
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> >>> On 08.05.15 at 11:07, <feng.wu@xxxxxxxxx> wrote:
>> > +static inline void setup_posted_irte(
>> > +    struct iremap_entry *new_ire, struct pi_desc *pi_desc, uint8_t gvec)
>> > +{
>> > +    new_ire->post.urg = 0;
>> > +    new_ire->post.vector = gvec;
>> > +    new_ire->post.pda_l = (((u64)virt_to_maddr(pi_desc)) >>
>> > +                           (32 - PDA_LOW_BIT)) & PDA_MASK(LOW);
>> > +    new_ire->post.pda_h = (((u64)virt_to_maddr(pi_desc)) >> 32) &
>> > +                           PDA_MASK(HIGH);
>> 
>> Looking at this another time I can't see what the and-ing with
>> PAD_MASK() is supposed to be good for. 
> 
> I cannot understand this well. Do you mean we don't need and PDA_MASK() 
> here?

Correct - the bitfield width (where the data gets stored into) already
enforces the intended truncation afaict.

Jan


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