On 4/4/2023 8:43 PM, Burakov, Anatoly wrote:
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On 2/7/2023 8:56 AM, Gupta, Nipun wrote:
[AMD Official Use Only - General]
Hi David,
I agree that change is not straightforward to review, but it should
not cause any functional issue as we are still creating all the memory
mappings, but one by one for each segment.
For hot plug case this causes issue as mentioned, that VFIO does not
allow unmap of the individual segments in case mapping was created of
a single coalesced segment.
But yes, I am not sure why this code was added, which Anatoly may have
more understanding on.
The motivation behind this code was that Linux allows limited amount of
page mappings, so we were trying to save on those. However, since then
there have been a few changes related to partial unmaps that may make it
so that this code is not only no longer necessary, but is in fact
actively harmful. I agree that this at least warrants a second look.
Anatoly,
Can you please provide your feedback on this change?
The patch probably shouldn't include the mailmap changes :)
Sure, will send a separate patch for it.
Could you please provide some steps to reproduce the hotplug issue
you're having? It would be great to have a test case for this patchset
to put it in context.
I am working on CDX bus
(http://patchwork.dpdk.org/project/dpdk/patch/20230124140746.594066-2-nipun.gu...@amd.com/)
and trying out some cases for plug/unplug.
The test is as follows:
# Run testpmd application
./dpdk-testpmd -c 0x3 -- -i --nb-cores=1
# Bind to VFIO
echo "vfio-cdx" > /sys/bus/cdx/devices/cdx-00\:00/driver_override
echo "cdx-00:00" > /sys/bus/cdx/drivers_probe
# Plug a device
testpmd> port attach cdx:cdx-00:00
#quit testpmd
testpmd> quit
This gave error at testpmd exit that memory cannot be freed. On
debugging I updated this code and seems it should be seen with any of
the device.
I see similar test case (without quit) mentioned
https://doc.dpdk.org/dts/test_plans/hotplug_test_plan.html, but the
difference is that it is with igb_uio and issue is being observed with VFIO.
Please note the device/bus mentioned in the commands is not yet
upstreamed in DPDK, but patches would be sent out soon.
Thanks,
Nipun
--
Thanks,
Anatoly
