On 2011-09-06 11:00, Sasha Levin wrote: > On Tue, 2011-09-06 at 10:49 +0200, Jan Kiszka wrote: >> On 2011-09-06 10:46, Sasha Levin wrote: >>> On Tue, 2011-09-06 at 10:36 +0200, Jan Kiszka wrote: >>>> On 2011-09-06 10:12, Michael S. Tsirkin wrote: >>>>> On Tue, Sep 06, 2011 at 10:52:41AM +0300, Avi Kivity wrote: >>>>>>> >>>>>>> BTW, the same is also true for that optional per-vector masking of >>>>>>> legacy MSI. Are there devices in the field that actually support this? I >>>>>>> haven't found one so far and tend to consider this feature not worth >>>>>>> implementing. >>>>>> >>>>>> Don't know. I don't like implementing features on the basis of bug >>>>>> reports, though. On the other hand we can't really test it without >>>>>> a real device. >>>>> >>>>> Linux will use this capability if present. So >>>>> we could add support for an emulated device (e.g. e1000), >>>>> then test with nested virt once iommu emulation lands :) >>>> >>>> Yeah, would be kind of cool. Still, I would feel better having it tested >>>> against a real silicon as well. Also to prove that there is a real need. >>>> >>>> So, in case someone stumbles for such a device (bit 8 set in MSI control >>>> word), please let us know! >>> >>> Doesn't any device that supports MSI-X supports per-vector masking? >>> >>> >From the spec: >>> >>> "MSI and MSI-X each support per-vector masking. Per-vector masking is an >>> optional extension to MSI, and a standard feature with MSI-X" >> >> Right, but the cap flag still has to be set. >> > > Are you sure? Take a look at the table in section 6.8.2.3 in the spec > (pci v3). Unlike the message control for MSI, this table doesn't mention > anything about bit 8 or the per-vector masking capability for MSI-X, it > just assumes it's there. [Err, I should stop doing n things in parallel.] Of course, MSI-X implies per-vector masking, but in a totally different way with different data structures etc. That's not interesting for the case in question: per-vector masking for legacy MSI. Back to square #1: We need a device with MSI support and cap bit 8 set in its _MSI_ control word. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- 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
