Re: [Qemu-ppc] [Qemu-devel] [PATCH] ohci: Stop OHCI bus when PCI bus master is disabled

[Alexey Kardashevskiy]

On 09/11/2014 05:22 PM, Gerd Hoffmann wrote:
> On Do, 2014-09-11 at 17:11 +1000, Alexey Kardashevskiy wrote:
>> When the guest performs kexec() (for example, as a part of kdump),
>> new kernel does PCI probing. As a part of it, PCI_COMMAND_MASTER
>> gets disabled which disables bus master memory region.
>> Since ohci_frame_boundary() timer is not stopped at this point
>> as OHCI device was not reset, the device tries accessing DMA memory,
>> fails and ends up in ohci_die() producing errors:
>>
>> usb-ohci: HCCA read error at 30000000
>> ohci_die: DMA error
> 
> Which is the correct behavior.
> 
> IMHO the kernel should stop ohci before doing kexec.


To be precise, it is kdump.

> Independant of that we can move the ohci error logging to tracepoints,
> so ohci emulation is silent by default.

That is the other way to go, yes.



-- 
Alexey