Hotadd pci devices

2009-10-04T07:31:35Z

Avishay: Changed bus 0 to 'auto' in examples: 0 causes segfault (https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/419590)

== Using PCI Hotplug Support ==
PCI Hotplug support is now available in kvm.git, here is how to use it.

== Install PCI Hotplug drivers in the guest (Linux) ==
I loaded the following modules to get pci hotplug working:
* acpiphp
* pci_hotplug

You can either add these to your distro's module list to load on boot, or run a command like this.

for m in acpiphp pci_hotplug; do sudo modprobe ${m}; done

== Use QEMU monitor to hot add devices ==

The QEMU monitor has a new command, '''pci_add''', which is used to hotadd the pci devices.

QEMU 0.9.1 monitor - type 'help' for more information
(qemu) help pci_add
pci_add bus nic|storage [[vlan=n][,macaddr=addr][,model=type]] [file=file][,if=type][,bus=nr]... -- hot-add PCI device

=== Add a NIC ===
The following command in the QEMU monitor hot-adds a nic to the guest.
* '''pci_add auto nic model=e1000'''
You can replace '''model=e1000''' with either '''model=rtl8139''', '''model=virtio''', or '''model=ne2k_pci'''. Note that '''model=ne2000''' isn't pci-based but rather ISA-based and cannot be used for hotplug.

(qemu) pci_add auto nic model=e1000 WARNING: PCI region size must be pow2 type=0x0, size=0x60000 OK bus 0, slot 5, function 0 (devfn 40)

In the guest we can check if the device was added by looking at dmesg.
[ 91.808265] acpiphp: Slot [30] registered
[ 91.808276] acpiphp: Slot [31] registered
[ 110.828130] PCI: Ignore bogus resource 6 [0:0] of 0000:00:02.0
[ 110.828333] decode_hpp: Could not get hotplug parameters. Use defaults
[ 110.903259] Intel(R) PRO/1000 Network Driver - version 7.3.20-k2-NAPI
[ 110.903264] Copyright (c) 1999-2006 Intel Corporation.
[ 110.903489] ACPI: PCI Interrupt Link [LNKA] enabled at IRQ 10
[ 110.903492] ACPI: PCI Interrupt 0000:00:05.0[A] -> Link [LNKA] -> GSI 10 (level, high) -> IRQ 10
[ 111.238713] e1000: 0000:00:05.0: e1000_probe: (PCI:33MHz:32-bit) 52:54:00:12:34:57
[ 111.292550] e1000: eth1: e1000_probe: Intel(R) PRO/1000 Network Connection

=== Add a disk ===
The following command in the QEMU monitor will add a scsi disk to the guest:
* '''pci_add auto storage file=/home/rharper/work/images/empty.img,if=scsi'''
You can replace '''if=scsi''' with '''if=virtio''', but IDE is not hotpluggable.

QEMU 0.9.1 monitor - type 'help' for more information
(qemu) pci_add auto storage file=/home/rharper/work/images/empty.img,if=scsi
OK bus 0, slot 5, function 0 (devfn 40)

In the guest we see via dmesg that the device was added.

[ 150.581752] PCI: Enabling device 0000:00:05.0 (0000 -> 0003)
[ 150.582634] ACPI: PCI Interrupt Link [LNKA] enabled at IRQ 10
[ 150.582637] ACPI: PCI Interrupt 0000:00:05.0[A] -> Link [LNKA] -> GSI 10 (level, high) -> IRQ 10
[ 150.585099] sym0: <895a> rev 0x0 at pci 0000:00:05.0 irq 10
[ 150.594628] sym0: No NVRAM, ID 7, Fast-40, LVD, parity checking
[ 150.607861] sym0: SCSI BUS has been reset.
[ 150.607883] scsi2 : sym-2.2.3
[ 153.608433] scsi 2:0:0:0: Direct-Access QEMU QEMU HARDDISK 0.9. PQ: 0 ANSI: 3
[ 153.608462] target2:0:0: tagged command queuingenabled, command queue depth 16.
[ 153.608484] target2:0:0: Beginning Domain Validation
[ 153.609517] target2:0:0: Domain Validation skipping write tests
[ 153.609522] target2:0:0: Ending Domain Validation
[ 153.618880] scsi 2:0:0:0: Attached scsi generic sg1 type 0
[ 153.749967] Driver 'sd' needs updating - please use bus_type methods
[ 153.750204] sd 2:0:0:0: [sda] 20971520 512-byte hardware sectors (10737 MB)
[ 153.750253] sd 2:0:0:0: [sda] Write Protect is off
[ 153.750255] sd 2:0:0:0: [sda] Mode Sense: 14 00 00 00
[ 153.750354] sd 2:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 153.750478] sd 2:0:0:0: [sda] 20971520 512-byte hardware sectors (10737 MB)
[ 153.750253] sd 2:0:0:0: [sda] Write Protect is off
[ 153.750255] sd 2:0:0:0: [sda] Mode Sense: 14 00 00 00
[ 153.750354] sd 2:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 153.750478] sd 2:0:0:0: [sda] 20971520 512-byte hardware sectors (10737 MB)
[ 153.750534] sd 2:0:0:0: [sda] Write Protect is off
[ 153.750536] sd 2:0:0:0: [sda] Mode Sense: 14 00 00 00
[ 153.750634] sd 2:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 153.750637] sda: unknown partition table
[ 153.759275] sd 2:0:0:0: [sda] Attached SCSI disk

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Hotadd pci devices