[SeaBIOS] [PATCH v1 0/2] virtio: finalize features before using modern device

[Xuan Zhuo]

https://www.mail-archive.com/[e-mail]/msg920776.html
Then:
$ build/qemu-system-x86_64 -M accel=kvm -m 1G -cpu host -blockdev
  file,node-name=drive0,filename=test.img -device
  virtio-blk-pci,drive=drive0
  qemu: queue_enable is only suppported in devices of virtio 1.0 or later.

In this PATCH, it was added to check the FEATURE VIRTIO_1 when enabling queue.
This code should not be executed, but it is reported here. Because Seabios
use the legacy sequence to initialize the modern device.

The driver MUST follow this sequence to initialize a device:
    1. Reset the device.
    2. Set the ACKNOWLEDGE status bit: the guest OS has noticed the device.
    3. Set the DRIVER status bit: the guest OS knows how to drive the device.
> Read device feature bits, and write the subset of feature bits understood by the OS and driver to the

device. During this step the driver MAY read (but MUST NOT write) the device-specific configuration
       fields to check that it can support the device before accepting it.
> Set the FEATURES_OK status bit. The driver MUST NOT accept new feature bits after this step.
> Re-read device status to ensure the FEATURES_OK bit is still set: otherwise, the device does not

support our subset of features and the device is unusable.
    7. Perform device-specific setup, including discovery of virtqueues for the device, optional per-bus setup,
       reading and possibly writing the device’s virtio configuration space, and population of virtqueues.
    8. Set the DRIVER_OK status bit. At this point the device is “live”.

Test with:

qemu-system-x86_64 \
       -M microvm,x-option-roms=off,pit=off,pic=off,isa-serial=off,rtc=off \
       -global virtio-mmio.force-legacy={false,true} \
       -enable-kvm -cpu host -m 512m -smp 2 \
       -nodefaults -no-user-config -nographic \
       -drive id=test,file=./test.img,format=raw,if=none \
       -device virtio-blk-device,drive=test \
       -bios ../../seabios/out/bios.bin \
       -chardev stdio,id=seabios -device isa-debugcon,iobase=0x402,chardev=seabios

qemu-system-x86_64 \
       -M microvm,x-option-roms=off,pit=off,pic=off,isa-serial=off,rtc=off \
       -global virtio-mmio.force-legacy={false,true} \
       -enable-kvm -cpu host -m 512m -smp 2 \
       -nodefaults -no-user-config -nographic \
       -drive id=test,file=./test.img,format=raw,if=none \
       -device virtio-scsi-device \
       -bios ../../seabios/out/bios.bin \
       -chardev stdio,id=seabios -device isa-debugcon,iobase=0x402,chardev=seabios

qemu-system-x86_64 \
       -enable-kvm -cpu host -m 512m -smp 2 \
       -nodefaults -no-user-config -nographic \
       -drive id=test,file=./test.img,format=raw,if=none \
       -device virtio-scsi,disable-legacy={off,on},disable-modern={on,off} \
       -bios ../../seabios/out/bios.bin \
       -chardev stdio,id=seabios -device isa-debugcon,iobase=0x402,chardev=seabios

qemu-system-x86_64 \
       -enable-kvm -cpu host -m 512m -smp 2 \
       -nodefaults -no-user-config -nographic \
       -drive id=test,file=./test.img,format=raw,if=none \
       -device virtio-blk-pci,drive=test,disable-legacy={off,on},disable-modern={on,off} \
       -bios ../../seabios/out/bios.bin \
       -chardev stdio,id=seabios -device isa-debugcon,iobase=0x402,chardev=seabios

Xuan Zhuo (2):
  virtio-mmio: read/write the hi 32 features for mmio
  virtio: finalize features before using device

src/hw/virtio-blk.c  | 22 +++++++++++++---------
 src/hw/virtio-pci.c  |  7 +++++--
 src/hw/virtio-scsi.c | 13 +++++++++++++
 3 files changed, 31 insertions(+), 11 deletions(-)