[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] [VTD][patch 0/5] HVM device assignment using vt-d
Base on my understanding of the Neocleus' passthrough patch, it seems all devices sharing that interrupt will get the double number of interrupts. This means if a interrupt is shared between a NIC device used by a HVM guest and a SATA device used by dom0, the SATA driver in dom0 will also get twice the number of interrupts. Am I correct? Allen >-----Original Message----- >From: Guy Zana [mailto:guy@xxxxxxxxxxxx] >Sent: Wednesday, May 30, 2007 11:05 PM >To: Keir Fraser; Kay, Allen M; xen-devel@xxxxxxxxxxxxxxxxxxx >Subject: RE: [Xen-devel] [VTD][patch 0/5] HVM device >assignment using vt-d > > >> -----Original Message----- >> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx >> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of >> Keir Fraser >> Sent: Wednesday, May 30, 2007 10:56 PM >> To: Kay, Allen M; xen-devel@xxxxxxxxxxxxxxxxxxx >> Subject: Re: [Xen-devel] [VTD][patch 0/5] HVM device >> assignment using vt-d >> > >> >> Actually I also know there are some other patches coming down >> the pipeline to do pci passthrough to HVM guests without need >> for hardware support (of course it is not so general; in >> particular it will only work for one special hvm guest). >> However, they deal with this interrupt issue quite cunningly, >> by inverting the interrupt polarity so that they get >> interrupts on both +ve and -ve edges of the INTx line. This >> allows the virtual interrupt wire to be 'wiggled' precisely >> according to the behaviour of the physical interrupt wire. >> Which is rather nice, although of course it does double the >> interrupt rate, which is not so great but perhaps acceptable >> for the kind of low interrupt rate devices that most people >> would want to hand off to a hvm guest. >> > >Just FYI. > >Neocleus' pass-through patches performs the "change polarity" trick. >With changing the polarity, our motivation was to reflect the >allocated device's assertion state to the HVM AS IS. > >Regarding the performance, using a USB 2.0 storage device >(working with DMA), a huge file copy was compared when working >in pass-through, and when working in native (on the same OS), >the time differences were negligible so I'm not sure yet about >the impact of doubling the number of interrupts. The advantage >of changing the polarity is the simplicity. > >Anyways, We'll release some patches during the day so you >could give your comments. > >Thanks, >Guy. > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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