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

["Michael S. Tsirkin" <mst@redhat.com>]

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 :)

-- 
MST