On Thu, 2011-08-25 at 17:40 +0300, Avi Kivity wrote: > On 08/25/2011 05:39 PM, Sasha Levin wrote: > > On Thu, 2011-08-25 at 17:00 +0300, Avi Kivity wrote: > > > On 08/25/2011 04:29 PM, Sasha Levin wrote: > > > > 2. The spec describes DOORBELL as an array of DWORDs, when one guest > > > > wants to poke a different guest it would write something into the offset > > > > of the other guest in the DOORBELL array. > > > > Looking at the implementation in QEMU, DOORBELL is one DWORD, when > > > > writing to it the upper WORD is the guest id and the lower WORD is the > > > > value. > > > > What am I missing here? > > > > > > > > > > The spec in qemu.git is accurate. The intent is to use an ioeventfd > > > bound into an irqfd so a write into the doorbell injects an interrupt > > > directly into the other guest, without going through qemu^Wkvm tool. > > > > > > > But the doorbell is a single DWORD, so if a guest writes to it we'd > > still need to figure out which guest/vector he wants to poke from > > userspace, no? > > > > If it was an array of doorbells then yes, we could assign an ioeventfd > > to each offset - but now I don't quite see how we can avoid passing > > through the userspace. > > > > Use the datamatch facility. > > We didn't want an array of registers to avoid scaling issues (PIO space > is quite small). > > Ah, right. Thanks! -- Sasha. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
