[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC v2 07/15] vt-d: Add API to update IRTE when VT-d PI is used
> -----Original Message----- > From: Jan Beulich [mailto:JBeulich@xxxxxxxx] > Sent: Monday, June 15, 2015 5:35 PM > To: Wu, Feng > Cc: andrew.cooper3@xxxxxxxxxx; george.dunlap@xxxxxxxxxxxxx; Tian, Kevin; > Zhang, Yang Z; xen-devel@xxxxxxxxxxxxx; keir@xxxxxxx > Subject: RE: [RFC v2 07/15] vt-d: Add API to update IRTE when VT-d PI is used > > >>> On 15.06.15 at 11:20, <feng.wu@xxxxxxxxx> wrote: > > > > >> -----Original Message----- > >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx] > >> Sent: Friday, June 12, 2015 6:35 PM > >> To: Wu, Feng > >> Cc: andrew.cooper3@xxxxxxxxxx; george.dunlap@xxxxxxxxxxxxx; Tian, Kevin; > >> Zhang, Yang Z; xen-devel@xxxxxxxxxxxxx; keir@xxxxxxx > >> Subject: RE: [RFC v2 07/15] vt-d: Add API to update IRTE when VT-d PI is > >> used > >> > >> >>> 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. > > > > We may not need PDA_MASK(HIGH), but is PDA_MASK(LOW) really > unnecessary > > here? > > I think so - iirc the bitfield is exactly the width you need (or if it > wasn't, that would be a mistake). What you can't get rid of is the > shifting. You are right. I got the same result after removing the PDA_MASK. Thanks, Feng > > Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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