How to share a directory with the host without networking in QEMU?
My problem is that networking devices in my device tree are not very stable so I thought the best way to share a folder between qemu and the host system is mount the same img without cache on both sides but the -hda option on qemu does not make the hd available in /dev/.
Here is the command I run.
./qemu-xilinx/arm-softmmu/qemu-system-arm -M xilinx-zynq-a9 -m 1024 -serial null -serial mon:stdio -dtb resources/devicetree.dtb -kernel resources/zImage -initrd resources.qemu/ramdisk.img -nographic -s
So the question is: is there a way to avoid networking and yet have a shared directory between qemu and the host?
EDIT: I compiled with
./configure --target-list="arm-softmmu,microblazeel-softmmu" --enable-fdt --disable-kvm --enable-virtfs
which should enable anything needed. However when I run
./qemu-xilinx/arm-softmmu/qemu-system-arm -M xilinx-zynq-a9 -m 1024 -serial null -serial mon:stdio -dtb /homes/cperivol/Sandbox/xilinx-zynq-bootstrap/resources/devicetree.dtb -kernel /homes/cperivol/Sandbox/xilinx-zynq-bootstrap/resources/zImage -initrd /homes/cperivol/Sandbox/xilinx-zynq-bootstrap/resources.qemu/ramdisk.img -nographic -s -fsdev local,path=/homes/cperivol/Sandbox/xilinx-zynq-bootstrap/qemu-sandbox/,security_model=passthrough,id=host0 -device virtio-9p-pci,fsdev=host0,mount_tag=host_tag0
or
./qemu-xilinx/arm-softmmu/qemu-system-arm -M xilinx-zynq-a9 -m 1024 -serial null -serial mon:stdio -dtb resources/devicetree.dtb -kernel resources/zImage -initrd resources.qemu/ramdisk.img -nographic -s -virtfs local,path=/homes/cperivol/Sandbox/xilinx-zynq-bootstrap/qemu-sandbox/,mount_tag=host0,security_model=passthrough,id=host0
I get
No 'PCI' bus found for device 'virtio-9p-pci'
Maybe I should also mention that in arm-softmmu/config-devices.mak there is CONFIG_PCI=y, and sure enough the object files of the pci are there in hw/pci.
EDIT2: Looking at the device tree as dumped by qemu the emulated system does not include a PCI bus.
(qemu) info qtree
bus: main-system-bus
type System
dev: xlnx.ps7-dev-cfg, id ""
irq 1
mmio 00000000f8007000/000000000000011c
dev: pl330, id ""
gpio-in 32
num_chnls = 8
num_periph_req = 4
num_events = 16
mgr_ns_at_rst = 0
i-cache_len = 4
num_i-cache_lines = 8
boot_addr = 0
INS = 0
PNS = 0
data_width = 64
wr_cap = 8
wr_q_dep = 16
rd_cap = 8
rd_q_dep = 16
data_buffer_dep = 256
irq 17
mmio 00000000f8003000/0000000000001000
dev: generic-sdhci, id ""
capareg = 0x5780080
maxcurr = 0x0
irq 1
mmio 00000000e0101000/0000000000000100
dev: generic-sdhci, id ""
capareg = 0x5780080
maxcurr = 0x0
irq 1
mmio 00000000e0100000/0000000000000100
dev: cadence_gem, id ""
mac = 52:54:00:12:34:56
vlan = 0
netdev = hub0port0
bootindex = -1
irq 1
mmio 00000000e000b000/0000000000000640
dev: cadence_ttc, id ""
irq 3
mmio 00000000f8002000/0000000000001000
dev: cadence_ttc, id ""
irq 3
mmio 00000000f8001000/0000000000001000
dev: cadence_uart, id ""
irq 1
mmio 00000000e0001000/0000000000001000
dev: cadence_uart, id ""
irq 1
mmio 00000000e0000000/0000000000001000
dev: xlnx.ps7-qspi, id ""
num-busses = 2
num-ss-bits = 1
num-txrx-bytes = 4
irq 3
mmio 00000000e000d000/0000000000000100
mmio 00000000fc000000/0000000002000000
bus: spi1
type SSI
dev: n25q128, id ""
gpio-in 1
bus: spi0
type SSI
dev: n25q128, id ""
gpio-in 1
dev: xlnx.ps7-spi, id ""
num-busses = 1
num-ss-bits = 4
num-txrx-bytes = 1
irq 5
mmio 00000000e0007000/0000000000000100
bus: spi0
type SSI
dev: n25q128, id ""
gpio-in 1
dev: n25q128, id ""
gpio-in 1
dev: n25q128, id ""
gpio-in 1
dev: n25q128, id ""
gpio-in 1
dev: xlnx.ps7-spi, id ""
num-busses = 1
num-ss-bits = 4
num-txrx-bytes = 1
irq 5
mmio 00000000e0006000/0000000000000100
bus: spi0
type SSI
dev: n25q128, id ""
gpio-in 1
dev: n25q128, id ""
gpio-in 1
dev: n25q128, id ""
gpio-in 1
dev: n25q128, id ""
gpio-in 1
dev: xlnx,ps7-usb, id "zynq-usb-1"
maxframes = 128
irq 1
mmio 00000000e0003000/0000000000001000
bus: zynq-usb-1.0
type usb-bus
dev: xlnx,ps7-usb, id "zynq-usb-0"
maxframes = 128
irq 1
mmio 00000000e0002000/0000000000001000
bus: zynq-usb-0.0
type usb-bus
dev: xlnx.ps7-i2c, id ""
irq 1
mmio 00000000e0005000/000000000000002c
bus: i2c
type i2c-bus
dev: pca9548, id ""
chip-enable = 0
address = 0
address-range = 128
reg = 0
bus: i2c@7
type i2c-bus
bus: i2c@6
type i2c-bus
bus: i2c@5
type i2c-bus
bus: i2c@4
type i2c-bus
bus: i2c@3
type i2c-bus
dev: at.24c08, id ""
size = 1024
address = 84
address-range = 4
reg = 84
dev: at.24c08, id ""
size = 1024
address = 80
address-range = 4
reg = 80
bus: i2c@2
type i2c-bus
dev: at.24c08, id ""
size = 1024
address = 84
address-range = 4
reg = 84
dev: at.24c08, id ""
size = 1024
address = 80
address-range = 4
reg = 80
bus: i2c@1
type i2c-bus
bus: i2c@0
type i2c-bus
dev: xlnx.ps7-i2c, id ""
irq 1
mmio 00000000e0004000/000000000000002c
bus: i2c
type i2c-bus
dev: pca9548, id ""
chip-enable = 0
address = 0
address-range = 128
reg = 0
bus: i2c@7
type i2c-bus
bus: i2c@6
type i2c-bus
bus: i2c@5
type i2c-bus
bus: i2c@4
type i2c-bus
bus: i2c@3
type i2c-bus
dev: at.24c08, id ""
size = 1024
address = 84
address-range = 4
reg = 84
dev: at.24c08, id ""
size = 1024
address = 80
address-range = 4
reg = 80
bus: i2c@2
type i2c-bus
dev: at.24c08, id ""
size = 1024
address = 84
address-range = 4
reg = 84
dev: at.24c08, id ""
size = 1024
address = 80
address-range = 4
reg = 80
bus: i2c@1
type i2c-bus
bus: i2c@0
type i2c-bus
dev: arm_mptimer, id ""
num-cpu = 1
irq 1
mmio ffffffffffffffff/0000000000000020
mmio ffffffffffffffff/0000000000000020
dev: arm_mptimer, id ""
num-cpu = 1
irq 1
mmio ffffffffffffffff/0000000000000020
mmio ffffffffffffffff/0000000000000020
dev: a9-scu, id ""
num-cpu = 1
irq 0
mmio ffffffffffffffff/0000000000000100
dev: arm_gic, id ""
gpio-in 96
num-cpu = 1
num-irq = 96
revision = 1
irq 1
mmio ffffffffffffffff/0000000000001000
mmio ffffffffffffffff/0000000000000100
mmio ffffffffffffffff/0000000000000100
dev: a9mpcore_priv, id ""
gpio-in 64
num-cpu = 1
num-irq = 96
irq 1
mmio 00000000f8f00000/0000000000002000
dev: xilinx,zynq_slcr, id ""
irq 0
mmio 00000000f8000000/0000000000001000
dev: nand, id ""
manufacturer_id = 32
chip_id = 170
drive = <null>
irq 0
dev: cfi.pflash02, id ""
drive = <null>
num-blocks = 512
sector-length = 131072
width = 1
mappings = 1
big-endian = 0
id0 = 102
id1 = 34
id2 = 0
id3 = 0
unlock-addr0 = 2730
unlock-addr1 = 1365
name = "pl353.pflash"
irq 0
mmio ffffffffffffffff/0000000004000000
dev: arm.pl35x, id ""
x = 3
irq 0
mmio 00000000e000e000/0000000000001000
mmio 00000000e2000000/0000000001000000
mmio 00000000e1000000/0000000001000000
Solution 1:
If the guest has 9p support (like Linux, or of course, Plan 9) and virtio, try adding the following switch.
-virtfs local,path=/path/to/share,mount_tag=host0,security_model=passthrough,id=host0
You may want to change the security_model parameter. See man page, qemu(1) for that. If I recall correctly, mount_tag is what the guest sees, leaving id as a dummy.
Make sure that the path is under the chroot if you are chrooting. It's a path to the directory on the host.
The fstab entry on the guest should look like this.
host0 /wherever 9p trans=virtio,version=9p2000.L 0 0
Either add that to your fstab, or invoke the appropriate command manually or using your init system, whatever it may be.
Solution 2:
Minimalist working 9P Buildroot setup for x86_64, arm and aarch64
I have created a highly automated Buildroot working setup that might help you diff out why your approach is not working.
The main ingredients are:
-
kernel settings:
CONFIG_9P_FS=y CONFIG_9P_FS_POSIX_ACL=y CONFIG_9P_FS_SECURITY=y CONFIG_NETWORK_FILESYSTEMS=y CONFIG_NET_9P=y CONFIG_NET_9P_DEBUG=y CONFIG_NET_9P_VIRTIO=yFor aarch64, also add:
CONFIG_PCI=y CONFIG_PCI_HOST_COMMON=y CONFIG_PCI_HOST_GENERIC=y CONFIG_VIRTIO_PCI=y CONFIG_VIRTIO_BLK=y CONFIG_VIRTIO_NET=yIf you forget to add the aarch64 configs, and
mountfails with:mount: mounting host0 on /mnt/my9p failed: Invalid argumentand dmesg complains with:
9pnet_virtio: no channels available for deviceDocumented at: https://wiki.qemu.org/Documentation/9psetup
-
my fstab entry and QEMU command were exactly as explained at: https://superuser.com/a/628381/128124
The manual mount command is:
mkdir /mnt/my9p mount -t 9p -o trans=virtio,version=9p2000.L host0 /mnt/my9pwhere
host0is the tag specified on the QEMU CLI.For reference, my full QEMU command lines are: x86:
./buildroot/output.x86_64~/host/usr/bin/qemu-system-x86_64 \ -m 128M \ -monitor telnet::45454,server,nowait \ -netdev user,hostfwd=tcp::45455-:45455,id=net0 \ -smp 1 \ -virtfs local,path=/host/path/to/share,mount_tag=host0,security_model=mapped,id=host0 \ -M pc \ -append 'root=/dev/vda nopat nokaslr norandmaps printk.devkmsg=on printk.time=y' \ -device edu \ -device lkmc_pci_min \ -device virtio-net-pci,netdev=net0 \ -kernel ./buildroot/output.x86_64~/images/bzImage \ -drive file='./buildroot/output.x86_64~/images/rootfs.ext2.qcow2,if=virtio,format=qcow2'arm:
./buildroot/output.arm~/host/usr/bin/qemu-system-arm -m 128M -monitor telnet::45454,server,nowait -netdev user,hostfwd=tcp::45455-:45455,id=net0 -smp 1 -virtfs local,path=/host/path/to/share,mount_tag=host0,security_model=mapped,id=host0 -M versatilepb -append 'root=/dev/sda nokaslr norandmaps printk.devkmsg=on printk.time=y' -device rtl8139,netdev=net0 -dtb ./buildroot/output.arm~/images/versatile-pb.dtb -kernel ./buildroot/output.arm~/images/zImage -serial stdio -drive file='./buildroot/output.arm~/images/rootfs.ext2.qcow2,if=scsi,format=qcow2'aarch64:
./buildroot/output.aarch64~/host/usr/bin/qemu-system-aarch64 -m 128M -monitor telnet::45454,server,nowait -netdev user,hostfwd=tcp::45455-:45455,id=net0 -smp 1 -virtfs local,path=/host/path/to/share,mount_tag=host0,security_model=mapped,id=host0 -M virt -append 'root=/dev/sda nokaslr norandmaps printk.devkmsg=on printk.time=y' -cpu cortex-a57 -device virtio-net-device,netdev=net0 -kernel ./buildroot/output.aarch64~/images/Image -nographic -serial stdio
Tested on QEMU 2.11 and guest Linux kernel 4.15.
I then also tested on Ubuntu 18.04 and it just worked: https://askubuntu.com/questions/884534/how-to-run-ubuntu-desktop-on-qemu/1046792#1046792