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

[Le Tan]

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?
Thanks again!

Regards,
Le

> --
> MST