On 10/14/2016 11:50 PM, Alex Williamson wrote:
On Fri, 14 Oct 2016 19:16:59 +0800
Cao jin <caoj.f...@cn.fujitsu.com> wrote:

When vfio device is reset(encounter FLR, or bus reset), if need to do
bus reset(vfio_pci_hot_reset_one is called), vfio_pci_pre_reset &
vfio_pci_post_reset will be called twice.

Signed-off-by: Cao jin <caoj.f...@cn.fujitsu.com>
Also has a little question on vfio_pci_reset. it will be called when encounter
bus reset, or FLR. The reset method's priority in this function now is:

     1. If has "device specific reset function", then do it
     2. If has FLR, then do it.
     3. If it can do bus reset(only 1 affected device), then do it
     4. If has pm_reset, then do it

The question is: why pm reset has low priority than bus reset(if it does
can do a bus reset)? why bus reset is not the last choice? In PCI driver
of kernel, pls see __pci_dev_reset, we can see, if device support pm reset,
it won't do bus reset.

The PCI spec doesn't really define what sort of reset is done with a PM
reset.  My thinking was that if a device advertises an FLR capability
then the hardware has made a concerted effort to have a per function
reset mechanism available.  NoSoftRst- is not terribly common and it's
not entirely clear to me that the hardware has made a conscious effort
to provide this for the purposes of per function reset mechanism.
Therefore I've opt'd to prioritize a bus reset over a PM reset.

I see, thanks for your infomation.

Yours Sincerely,

Cao jin

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