On Thu, Apr 26, 2018 at 04:34:50PM -0400, Sinan Kaya wrote:

Hi Greg,

Upstream commit 821cdad5c46c ("PCI: Wait up to 60 seconds for device to become ready after FLR") fixes a virtualization issue for Intel 750 NVMe drive and potentially other PCIe devices taking longer to recover from functional resets.

problem description below from the commit:

'Sporadic reset issues have been observed with an Intel 750 NVMe drive while assigning the physical function to the guest machine. The sequence of events observed is as follows:

• perform a Function Level Reset (FLR)
• sleep up to 1000ms total
• read ~0 from PCI_COMMAND (CRS completion for config read)
• warn that the device didn't return from FLR
• touch the device before it's ready
• device drops config writes when we restore register settings (there's no mechanism for software to learn about CRS completions for writes)
• incomplete register restore leaves device in inconsistent state
• device probe fails because device is in inconsistent state

After reset, an endpoint may respond to config requests with Configuration Request Retry Status (CRS) to indicate that it is not ready to accept new requests. See PCIe r3.1, sec 2.3.1 and 6.6.2.'

Please apply commit 821cdad5c46c to fix the resulting regression.

Looks good, but it's not really a "regression" as it didn't work at all before this patch :)

Now queued up.

greg k-h