Re: [libvirt] [RFC PATCH] support multifunction PCI device

On Wed, 11 May 2011 08:55:56 +0100 "Daniel P. Berrange" <berrange(a)redhat.com&gt; wrote: > On Wed, May 11, 2011 at 10:30:43AM +0800, Wen Congyang wrote: >> >> 3. After hot plug multi function PCI devices: >> # lspci >> 00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02) >> 00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II] >> 00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II] >> 00:01.2 USB Controller: Intel Corporation 82371SB PIIX3 USB [Natoma/Triton II] (rev 01) >> 00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03) >> 00:02.0 VGA compatible controller: Cirrus Logic GD 5446 >> 00:03.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 20) >> 00:04.0 RAM memory: Red Hat, Inc Virtio memory balloon >> 00:05.0 SCSI storage controller: LSI Logic / Symbios Logic 53c895a >> 00:06.0 SCSI storage controller: LSI Logic / Symbios Logic 53c895a >> 00:06.1 SCSI storage controller: LSI Logic / Symbios Logic 53c895a >> 00:06.2 SCSI storage controller: LSI Logic / Symbios Logic 53c895a >> 00:06.3 SCSI storage controller: LSI Logic / Symbios Logic 53c895a >> 00:06.4 SCSI storage controller: LSI Logic / Symbios Logic 53c895a >> 00:06.5 SCSI storage controller: LSI Logic / Symbios Logic 53c895a >> 00:06.6 SCSI storage controller: LSI Logic / Symbios Logic 53c895a >> 00:06.7 SCSI storage controller: LSI Logic / Symbios Logic 53c895a >> >> >>> >>>> >>>> 2. support to hot unplug multi function PCI device >>>> hot unpluging multi function PCI device meas that all the other >>>> devices on the same slot will be hot unpluged. So we should do >>>> some cleanup and remove the other devices too. If the other >>>> device on the same slot does not support hot unpluged, or it is a >>>> a controller and some other devices still use this controller, >>>> I think we should refuse to hot unplug this mutlti function PCI >>>> device. >>> >>> IMHO these kind of restrictions will make life really unpleasant >>> for applications and are a reason we should *not* support the >>> multifunction code. Instead we should focus on one of the other >>> 3 options I mention above. >> Hmm, how about adding <unpluggable> attribute to <device> definitions ? IIUC, 1. There are some unpluggable default devices. 2. There are devices which never should be removed by mistake, as rootfs. When I've google'd "how to handle 100+ nics with KVM", a qemu community guy answers "please use multifunction devices" but I disappointed to know libvirt doesn't support it, now. And, IIUC, if multifunction device is supporetd by libvirt, it can tie up default 'unpluggable' devices (as serial, IDE, etc) into a slot and we'll have 3? more empty slot at boot..

Thanks, -Kame