Avi Kivity wrote: > Marcelo Tosatti wrote: > >> Add three PCI bridges to support 128 slots. >> >> Changes since v1: >> - Remove I/O address range "support" (so standard PCI I/O space is used). >> - Verify that there's no special quirks for 82801 PCI bridge. >> - Introduce separate flat IRQ mapping function for non-SPARC targets. >> >> >> > > I've cooled off on the 128 slot stuff, mainly because most real hosts > don't have them. An unusual configuration will likely lead to problems > as most guest OSes and workloads will not have been tested thoroughly > with them. > > - it requires a large number of interrupts, which are difficult to > provide, and which it is hard to ensure all OSes support. MSI is > relatively new. > - is only a few interrupts are available, then each interrupt requires > scanning a large number of queues > > If we are to do this, then we need better tests than "80 disks show up". > > The alternative approach of having the virtio block device control up to > 16 disks allows having those 80 disks with just 5 slots (and 5 > interrupts). This is similar to the way traditional SCSI controllers > behave, and so should not surprise the guest OS. >
If you have a single virtio-blk device that shows up as 8 functions, we could achieve the same thing. We can cheat with the interrupt handlers to avoid cache line bouncing too. Plus, we can use PCI hotplug so we don't have to reinvent a new hotplug mechanism. I'm inclined to think that ring sharing isn't as useful as it seems as long as we don't have indirect scatter gather lists. Regards, Anthony Liguori ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
