Re: [Qemu-devel] vfio in the guest: no available reset mechanism

[Le Tan]

Hi Alex,

2014-07-30 22:46 GMT+08:00 Alex Williamson <address@hidden>:
> On Wed, 2014-07-30 at 22:16 +0800, Le Tan wrote:
>> Hi Michael,
>>
>> 2014-07-30 21:16 GMT+08:00 Michael S. Tsirkin <address@hidden>:
>> > On Wed, Jul 30, 2014 at 08:24:04PM +0800, Le Tan wrote:
>> >> Hi,
>> >> I am testing vfio in L1 with my VT-d emulation project. I assigned one
>> >> of the two AHCI controllers in L1 to L2 via vfio. After I ran the QEMU
>> >> in L1, it complains that:
>> >> qemu-system-x86_64: vfio: Cannot reset device 0000:00:03.0, no
>> >> available reset mechanism.
>> >> qemu-system-x86_64: vfio: Cannot reset device 0000:00:03.0, no
>> >> available reset mechanism.
>> >>
>> >> Then L2 paused when the SeaBIOS executed in ahci_controller_setup(). I
>> >> look into this and found that:
>> >> val = ahci_ctrl_readl(ctrl, HOST_CTL);
>> >> ahci_ctrl_writel(ctrl, HOST_CTL, val | HOST_CTL_AHCI_EN);
>> >> When the BIOS tried to read the HOST_CTL, it returns 0x80000002, which
>> >> bit 2 (Interrupt Enable) is 1. The AHCI manual says that this bit
>> >> should be cleared by default. So maybe L1 didn't reset the device
>> >> before assigning it to L2?
>> >> Then the BIOS tried to write back to HOST_CTL and it was stuck here. :(
>> >>
>> >> So can anyone give me some advice? About the state of PCI device or
>> >> bus-level reset?
>> >>
>> >> Here is the detail of the environment and the way I did the vfio.
>> >> 1. lspci in L1 said:
>> >> 00:03.0 SATA controller [0106]: Intel Corporation 82801IR/IO/IH
>> >> (ICH9R/DO/DH) 6 port SATA Controller [AHCI mode] [8086:2922] (rev 02)
>> >> 00:1f.0 ISA bridge [0601]: Intel Corporation 82801IB (ICH9) LPC
>> >> Interface Controller [8086:2918] (rev 02)
>> >> 00:1f.2 SATA controller [0106]: Intel Corporation 82801IR/IO/IH
>> >> (ICH9R/DO/DH) 6 port SATA Controller [AHCI mode] [8086:2922] (rev 02)
>> >> 00:1f.3 SMBus [0c05]: Intel Corporation 82801I (ICH9 Family) SMBus
>> >> Controller [8086:2930] (rev 02)
>> >> 2. Unbind 00:03.0 and do vfio:
>> >> modprobe -r vfio_iommu_type1
>> >> modprobe vfio_iommu_type1 allow_unsafe_interrupts=1
>> >> modprobe vfio-pci
>> >> echo 0000:00:03.0 > /sys/bus/pci/devices/0000\:00\:03.0/driver/unbind
>> >> echo "8086 2922" > /sys/bus/pci/drivers/vfio-pci/new_id
>> >> 3. run L2 with "-device vfio-pci,host=00:03.0"
>> >>
>> >> Any help is appreciated! Thanks very much!
>> >>
>> >> Regards,
>> >> Le
>> >
>> > Clearly, bus level reset can't work for the root bus :)
>>
>> Thanks very much!
>> I test the vfio with a second-bus ahci controller and it didn't
>> complain about the lack of reset mechanism. :) And the return val of
>> HOST_CTL is normal now (the same as emulated ahci controller).
>> However, it still paused when the BIOS tried to write to the HOST_CTL.
>> Do you have any idea?
>> And we should just test vfio and legacy pci-assignment with second bus
>> devices, not considering the root-bus devices?
>
> AHCI seems like a poor choice of device for this work, they typically
> don't support any kind of reset and they can be troublesome even for the
> L1 assignment.  You really want something with FLR support so that both
> the host and L1 guest can potentially reset the device.  That said, you
> may still run into bugs with a L1 guest directed FLR.  Thanks,
>
> Alex
>

So what device do you think is suitable for the pci-assign test? e1000?
I just tested it with sound card ac97 and USB controller. But I don't
know how to attach them to a pcie-to-pci bridge, so maybe they weren't
reset before being assigned to L2. But it seems that they can work.
1. With the sound card, I assigned it to L2 via both vfio and legacy
pci-assign and I could hear the music played in L2 from host's
speakers. Of course, the vfio also complained about the lack of reset
mechanism.
2. With the USB controller, I used "-usb -usbdevice disk:file" to
attach a USB disk to L1. But there were 4 related devices in L1, so I
didn't know what should be assigned to L2. the info qtree was like
this:
 dev: ich9-usb-uhci3, id ""
        masterbus = "usb-bus.0"
        firstport = 4 (0x4)
        bandwidth = 1280 (0x500)
        maxframes = 128 (0x80)
        addr = 1d.2
dev: ich9-usb-uhci2, id ""
        masterbus = "usb-bus.0"
        firstport = 2 (0x2)
        bandwidth = 1280 (0x500)
        maxframes = 128 (0x80)
        addr = 1d.1
 dev: ich9-usb-uhci1, id ""
        masterbus = "usb-bus.0"
        firstport = 0 (0x0)
        bandwidth = 1280 (0x500)
        maxframes = 128 (0x80)
        addr = 1d.0
dev: ich9-usb-ehci1, id ""
        maxframes = 128 (0x80)
        addr = 1d.7
         bus: usb-bus.0
          type usb-bus
          dev: usb-storage, id ""
            drive = ""
            logical_block_size = 512 (0x200)
            physical_block_size = 512 (0x200)
            min_io_size = 0 (0x0)
            opt_io_size = 0 (0x0)
            bootindex = -1 (0xffffffffffffffff)
            discard_granularity = 4294967295 (0xffffffff)
            removable = false
            port = ""
            serial = ""
            full-path = true
            msos-desc = true
            addr 0.1, port 1, speed 480, name QEMU USB MSD, attached
            bus: scsi.0
              type SCSI
              dev: scsi-disk, id ""
                drive = "usb0"
                logical_block_size = 512 (0x200)
                physical_block_size = 512 (0x200)
                min_io_size = 0 (0x0)
                opt_io_size = 0 (0x0)
Then I tried to unbind and bind both 1d.7 and 1d.0. Then I assigned
1d.0 to L2. L2 could boot smoothly and I could mount and access the
USB disk.
So what do you think?

Thanks very much.

Le