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Hot plugging devices
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hotplug.md

Hot plugging devices using ACPI, SHPC and native

This gist is to show different ways to hot plug devices in a Virtual Machine

Set up the environment

Create a device mapper

dd if=/dev/zero of=devmap.img count=1 bs=50M
fdisk devmap.img
	# Command (m for help): g
	# Command (m for help): n
	# Partition number (1-128, default 1): <RETURN>
	# First sector (2048-102366, default 2048): <RETURN>
	# Last sector, +sectors or +size{K,M,G,T,P} (2048-102366, default 102366): <RETURN>
	# Command (m for help): w
fdisk -l devmap.img
	# Disk devmap.img: 50 MiB, 52428800 bytes, 102400 sectors
sudo partx -av devmap.img
	# /dev/loop0: partition #1 added
sudo mkfs.ext4 /dev/loop0p1
sudo dmsetup create devmap --table '0 102400 linear /dev/loop0 0'

Do not forget remove it once you finish with your tests

ls -l /dev/mapper/devmap
	#  /dev/mapper/devmap -> ../dm-4
sudo dmsetup remove -f /dev/dm-4
sudo partx -d /dev/loop4

Setup environment variables

export KERNEL_CMDLINE="root=/dev/pmem0p1 rootflags=dax,data=ordered,errors=remount-ro rw rootfstype=ext4 \
tsc=reliable no_timer_check rcupdate.rcu_expedited=1 pci=lastbus=0 i8042.direct=1 i8042.dumbkbd=1 i8042.nopnp=1 \
i8042.noaux=1 noreplace-smp noacpi noapic reboot=k panic=1 console=hvc0 console=hvc1 initcall_debug iommu=off \
cryptomgr.notests net.ifnames=0 console=ttyS0"
export Q35_ACCEL="kvm,kernel_irqchip,nvdimm,nosmm,nosmbus,nosata,nopit,static-prt,nofw"

Get and build tools

clear containers qemu 2.9

compared with qemu upstream this version of qemu offers us two extra machine accelerators static-prt and nofw

git clone https://github.com/clearcontainers/qemu ;
git checkout qemu-lite-v2.9.0 ;
pushd qemu ;
curl https://raw.githubusercontent.com/clearcontainers/packaging/master/qemu-lite/configure.patch | patch -p1 ;
./configure --disable-static --disable-bluez --disable-brlapi --disable-bzip2 --disable-curl \
--disable-curses --disable-debug-tcg --disable-fdt --disable-glusterfs --disable-gtk \
--disable-libiscsi --disable-libnfs --disable-libssh2 --disable-libusb --disable-linux-aio \
--disable-lzo --disable-opengl --disable-qom-cast-debug --disable-rbd --disable-rdma --disable-sdl \
--disable-seccomp --disable-slirp --disable-snappy --disable-spice --disable-strip \
--disable-tcg-interpreter --disable-tcmalloc --disable-tools --disable-tpm --disable-usb-redir \
--disable-uuid --disable-vnc --disable-vnc-jpeg --disable-vnc-png --disable-vnc-sasl --disable-vte \
--disable-xen --enable-attr --enable-cap-ng --enable-kvm --enable-virtfs \
--target-list=x86_64-softmmu --extra-cflags="-fno-semantic-interposition -O3 -falign-functions=32" \
--datadir=/usr/share/qemu-lite --libdir=/usr/lib64/qemu-lite --libexecdir=/usr/libexec/qemu-lite \
--enable-vhost-net --disable-docs ;
cp x86_64-softmmu/qemu-system-x86_64 ../qemu-lite-system-x86_64-2.9.0
popd

linux container kernel

Patches (Only for SHPC)

Configs

for SHPC

  • CONFIG_HOTPLUG_PCI_PCIE=y
  • CONFIG_HOTPLUG_PCI=y
  • CONFIG_HOTPLUG_PCI_CPCI=y
  • CONFIG_HOTPLUG_PCI_SHPC=y

for native hotplug

  • CONFIG_HOTPLUG_PCI_PCIE=y
  • CONFIG_PCIEAER=y
  • CONFIG_PCIEASPM=y
  • CONFIG_PCIEASPM_DEFAULT=y
  • CONFIG_HOTPLUG_PCI=y
  • CONFIG_RAS=y

qboot

git clone https://github.com/bonzini/qboot
make

CBFS linux kernel

dd if=/dev/zero of=boot.bin bs=4096 count=1
cbfstool cbfs.rom create -s 8128k -B boot.bin -m x86 -o 0x1000
cbfstool cbfs.rom add -f vmlinuz-4.9.47-77.container -n vmlinuz -t raw
echo ${KERNEL_CMDLINE} > cmdline
cbfstool cbfs.rom add -f cmdline -n cmdline -t raw

Native hot plug

q35 + vmlinux + nofw

Start a new VM

./qemu-lite-system-x86_64-2.9.0 -machine q35,accel=${Q35_ACCEL} -cpu host -device \
nvdimm,id=nv0,memdev=mem0 -object memory-backend-file,id=mem0,mem-path=containers.img,size=471859200 \
-m 2048M,slots=2,maxmem=16998M -smp 4,cores=4,threads=1,sockets=1 -vga none -nographic \
-no-user-config -nodefaults -kernel vmlinux.container -append "${KERNEL_CMDLINE}" -device \
virtio-serial-pci,id=virtio-serial0 -chardev stdio,id=charconsole0,signal=off -device \
virtconsole,chardev=charconsole0,id=console0 -enable-kvm -qmp unix:hypervisor.sock,server,nowait \
-device pcie-root-port,id=root1

Hot plugging virtio disk

echo '{ "execute": "qmp_capabilities" }
{ "execute": "blockdev-add", "arguments":{"driver":"raw","node-name":"disk1", "file":{"driver":"file","filename":"/dev/mapper/devmap"}}}
{ "execute": "device_add", "arguments": { "driver": "virtio-blk", "drive": "disk1", "id": "virtio0", "bus": "root1", "bootindex": "1" } }' |
socat - unix-connect:hypervisor.sock

log message example

[   11.391260] pciehp 0000:00:02.0:pcie004: Slot(0): Attention button pressed
[   11.391382] pciehp 0000:00:02.0:pcie004: Slot(0): Card present
[   11.391512] pciehp 0000:00:02.0:pcie004: Slot(0) Powering on due to button press
[   12.516403] pci 0000:01:00.0: BAR 4: assigned [mem 0xf00000000-0xf00003fff 64bit pref]
[   12.516712] pci 0000:01:00.0: BAR 1: assigned [mem 0xc0000000-0xc0000fff]
[   12.516874] pcieport 0000:00:02.0: PCI bridge to [bus 01]
[   12.517008] pcieport 0000:00:02.0:   bridge window [io  0x1000-0x1fff]
[   12.518776] pcieport 0000:00:02.0:   bridge window [mem 0xc0000000-0xc01fffff]
[   12.520490] pcieport 0000:00:02.0:   bridge window [mem 0xf00000000-0xf001fffff 64bit pref]
[   12.523949] virtio-pci 0000:01:00.0: enabling device (0000 -> 0002)
[   12.527777]  vda: vda1

Hot plugging virtio net

echo '{ "execute": "qmp_capabilities" }
{ "execute": "device_add", "arguments": { "driver": "virtio-net-pci", "id": "virtio-net1", "bus": "root1" } }' |
socat - unix-connect:hypervisor.sock

log message example

[   11.827202] pciehp 0000:00:02.0:pcie004: Slot(0): Attention button pressed
[   11.827342] pciehp 0000:00:02.0:pcie004: Slot(0): Card present
[   11.827474] pciehp 0000:00:02.0:pcie004: Slot(0) Powering on due to button press
[   12.962931] pci 0000:01:00.0: BAR 4: assigned [mem 0xf00000000-0xf00003fff 64bit pref]
[   12.963436] pci 0000:01:00.0: BAR 1: assigned [mem 0xc0000000-0xc0000fff]
[   12.963704] pcieport 0000:00:02.0: PCI bridge to [bus 01]
[   12.963899] pcieport 0000:00:02.0:   bridge window [io  0x1000-0x1fff]
[   12.966579] pcieport 0000:00:02.0:   bridge window [mem 0xc0000000-0xc01fffff]
[   12.968503] pcieport 0000:00:02.0:   bridge window [mem 0xf00000000-0xf001fffff 64bit pref]
[   12.970227] virtio-pci 0000:01:00.0: enabling device (0000 -> 0002)

Hot plugging virtio serial port

To hot plug a virtio serial port PCI is not needed

echo '{ "execute": "qmp_capabilities" }
{ "execute" : "chardev-add", "arguments" : { "id" : "charch1", "backend" : { "type" : "socket", "data" : {"wait": false, "server": true, "addr": { "type": "unix", "data": { "path": "tty.sock" } } } } } }
{ "execute": "device_add", "arguments": { "driver": "virtserialport", "chardev":"charch1", "id": "channel1", "name": "sh.hyper.channel.1" } }' |
socat - unix-connect:hypervisor.sock

Native hot plug (PCIe switch)

q35 + vmlinux + nofw

Start a new VM

./qemu-lite-system-x86_64-2.9.0 -machine q35,accel=${Q35_ACCEL} -cpu host -device \
nvdimm,id=nv0,memdev=mem0 -object memory-backend-file,id=mem0,mem-path=containers.img,size=471859200 \
-m 2048M,slots=2,maxmem=16998M -smp 4,cores=4,threads=1,sockets=1 -vga none -nographic \
-no-user-config -nodefaults -kernel vmlinux.container -append "${KERNEL_CMDLINE}" -device \
virtio-serial-pci,id=virtio-serial0 -chardev stdio,id=charconsole0,signal=off -device \
virtconsole,chardev=charconsole0,id=console0 -enable-kvm -qmp unix:hypervisor.sock,server,nowait \
-device ioh3420,id=root1,chassis=1,slot=1

Hot plugging virtio disk

echo '{ "execute": "qmp_capabilities" }
{ "execute": "device_add", "arguments": { "driver": "xio3130-downstream", "id": "downstream1", "bus": "root1", "chassis": "0", "slot": "0" } }' |
socat - unix-connect:hypervisor.sock

echo '{ "execute": "qmp_capabilities" }
{ "execute": "blockdev-add", "arguments":{"driver":"raw","node-name":"disk1", "file":{"driver":"file","filename":"/dev/mapper/devmap" } } }
{ "execute": "device_add", "arguments": { "driver": "virtio-blk", "drive": "disk1", "id": "virtio1", "bus": "downstream1", "bootindex": "0" } }' |
socat - unix-connect:hypervisor.sock

ACPI hot plug

pc + vmlinuz

Start a new VM

./qemu-lite-system-x86_64-2.9.0 -machine pc,accel=kvm,kernel_irqchip,nvdimm -cpu host -device \
nvdimm,id=nv0,memdev=mem0 -object memory-backend-file,id=mem0,mem-path=clear-containers.img,size=471859200 \
-m 2048M,slots=2,maxmem=16998M -smp 4,cores=4,threads=1,sockets=1 -vga none -nographic \
-no-user-config -nodefaults -kernel vmlinuz.container -append "${KERNEL_CMDLINE}" -device \
virtio-serial-pci,id=virtio-serial0 -chardev stdio,id=charconsole0,signal=off -device \
virtconsole,chardev=charconsole0,id=console0 -enable-kvm -qmp unix:hypervisor.sock,server,nowait

Hot plugging virtio disk

echo '{ "execute": "qmp_capabilities" }
{ "execute": "blockdev-add", "arguments":{"driver":"raw","node-name":"disk1", "file":{"driver":"file","filename":"/dev/mapper/devmap" } } }
{ "execute": "device_add", "arguments": { "driver": "virtio-blk", "drive": "disk1", "id": "virtio1", "bus": "pci.0", "bootindex": "1" } }' |
socat - unix-connect:hypervisor.sock

to detect the block device the pci bus MUST be re-scanned inside the VM

echo 1 > /sys/bus/pci/rescan

log message example

[   34.328712] pci 0000:00:04.0: BAR 4: assigned [mem 0x80000000-0x80003fff 64bit pref]
[   34.329176] pci 0000:00:04.0: BAR 1: assigned [mem 0x80004000-0x80004fff]
[   34.329612] pci 0000:00:04.0: BAR 0: assigned [io  0x1000-0x103f]
[   34.329947] pci 0000:00:03.0: PCI bridge to [bus 01]
[   34.332923] virtio-pci 0000:00:04.0: enabling device (0000 -> 0003)
[   34.350844] ACPI: PCI Interrupt Link [LNKD] enabled at IRQ 11
[   34.353554]  vda: vda1

ACPI hot plug (pci-bridge)

pc + vmlinuz

Start a new VM

./qemu-lite-system-x86_64-2.9.0 -machine pc,accel=kvm,kernel_irqchip,nvdimm -cpu host -device \
nvdimm,id=nv0,memdev=mem0 -object memory-backend-file,id=mem0,mem-path=clear-containers.img,size=471859200 \
-m 2048M,slots=2,maxmem=16998M -smp 4,cores=4,threads=1,sockets=1 -vga none -nographic \
-no-user-config -nodefaults -kernel vmlinuz.container -append "${KERNEL_CMDLINE}" -device \
virtio-serial-pci,id=virtio-serial0 -chardev stdio,id=charconsole0,signal=off -device \
virtconsole,chardev=charconsole0,id=console0 -enable-kvm -qmp unix:hypervisor.sock,server,nowait \
-device pci-bridge,id=root1,chassis_nr=1

Hot plugging virtio disk

echo '{ "execute": "qmp_capabilities" }
{ "execute": "blockdev-add", "arguments":{"driver":"raw","node-name":"disk1", "file":{"driver":"file","filename":"/dev/mapper/devmap" } } }
{ "execute": "device_add", "arguments": { "driver": "virtio-blk", "drive": "disk1", "id": "virtio1", "bus": "root1", "bootindex": "1" } }' |
socat - unix-connect:hypervisor.sock

to detect the block device the pci bus MUST be re-scanned inside the VM

echo 1 > /sys/bus/pci/rescan

log message example

[   28.189942] pci 0000:00:03.0: BAR 8: assigned [mem 0x80000000-0x800fffff]
[   28.190097] pci 0000:00:03.0: BAR 9: assigned [mem 0x80100000-0x801fffff 64bit pref]
[   28.190202] pci 0000:00:03.0: BAR 7: assigned [io  0x1000-0x1fff]
[   28.190287] pci 0000:01:00.0: BAR 4: assigned [mem 0x80100000-0x80103fff 64bit pref]
[   28.190505] pci 0000:01:00.0: BAR 1: assigned [mem 0x80000000-0x80000fff]
[   28.190651] pci 0000:01:00.0: BAR 0: assigned [io  0x1000-0x103f]
[   28.190785] pci 0000:00:03.0: PCI bridge to [bus 01]
[   28.190892] pci 0000:00:03.0:   bridge window [io  0x1000-0x1fff]
[   28.192473] pci 0000:00:03.0:   bridge window [mem 0x80000000-0x800fffff]
[   28.193584] pci 0000:00:03.0:   bridge window [mem 0x80100000-0x801fffff 64bit pref]
[   28.197029] virtio-pci 0000:01:00.0: enabling device (0000 -> 0003)
[   28.215856] ACPI: PCI Interrupt Link [LNKC] enabled at IRQ 11
[   28.219026]  vda: vda1

ACPI hot plug several devices

q35 + nofw + vmlinux

Start a new VM

./qemu-lite-system-x86_64-2.9.0 -machine q35,accel=$Q35_ACCEL -cpu host -device \
nvdimm,id=nv0,memdev=mem0 -object memory-backend-file,id=mem0,mem-path=clear-containers.img,size=471859200 \
-m 2048M,slots=2,maxmem=16998M -smp 4,cores=4,threads=1,sockets=1 -vga none -nographic \
-no-user-config -nodefaults -kernel vmlinux.container -append "$KERNEL_CMDLINE" \
-device virtio-serial-pci,id=virtio-serial0 -chardev stdio,id=charconsole0,signal=off -device \
virtconsole,chardev=charconsole0,id=console0 -enable-kvm -qmp unix:hypervisor.sock,server,nowait \
-device pci-bridge,bus=pcie.0,id=root1,addr=2,chassis_nr=1,shpc=on

Hot plugging N virtio disks

There is a limit of 30 devices per PCI bridge

for i in $(seq 1 30); do
    echo '{ "execute": "qmp_capabilities" }
    { "execute": "blockdev-add", "arguments":{"driver":"raw", "node-name": "disk'$i'", "file":      {"driver":"file","filename":"/dev/mapper/devmap" } } }
    { "execute": "device_add", "arguments": { "driver": "virtio-blk", "drive": "disk'$i'", "id": "virtio'$i'",  "bus": "root1", "bootindex": "'$i'", "addr": "'$(printf "0x%x" $i)'" } }' |
    socat - unix-connect:hypervisor.sock;
done

to detect the block device the pci bus MUST be re-scanned inside the VM

echo 1 > /sys/bus/pci/rescan

Reference

pcie_pci_bridge.txt

pcie.txt

Q35.pdf

@mcastelino
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Adding qemu docu links
https://github.com/qemu/qemu/blob/master/docs/pcie_pci_bridge.txt
https://github.com/qemu/qemu/blob/master/docs/pcie.txt

@mcastelino
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A slightly more user friendly command line which gives you a command prompt

sudo ./x86_64-softmmu/qemu-system-x86_64 -machine q35,accel=kvm,kernel_irqchip,nvdimm \
-m 256,maxmem=512M,slots=2 -smp 2 -nodefaults -rtc base=utc,driftfix=slew \
-global kvm-pit.lost_tick_policy=discard \
-kernel ./vmlinuz.container  \
-append "reboot=k panic=1 rw tsc=reliable no_timer_check noreplace-smp root=/dev/pmem0p1 init=/usr/lib/systemd/systemd initcall_debug rootfstype=ext4 rootflags=dax,data=ordered dhcp rcupdate.rcu_expedited=1 clocksource=kvm-clock console=hvc0 single iommu=false pci=lastbus=0 nivablecore=20G debug" \
-device virtio-serial-pci,id=virtio-serial0 -chardev stdio,id=charconsole0 \
-device virtconsole,chardev=charconsole0,id=console0 -nographic \
-object memory-backend-file,id=mem0,share,mem-path=./clear-containers.img,size=235929600 \
-device nvdimm,memdev=mem0,id=nv0 -no-reboot \
-net nic,model=virtio \
-net user \
-qmp unix:hypervisor.sock,server,nowait \
-device ioh3420,bus=pcie.0,id=rp3 -device pcie-pci-bridge,id=br3,bus=rp3 \

@gorozco1
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Adding q35 presentation link:
https://wiki.qemu.org/images/4/4e/Q35.pdf

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