To: "Mo, YufengX" <yufengx...@intel.com>, dev@dpdk.org
From: "Burakov, Anatoly" <anatoly.bura...@intel.com>
Date: 06/26/2019 06:43PM
Cc: d...@ibm.com, prad...@us.ibm.com, Takeshi Yoshimura
<t...@jp.ibm.com>
Subject: [EXTERNAL] Re: [dpdk-dev] [PATCH] vfio: fix expanding DMA
area in ppc64le
On 18-Jun-19 3:37 AM, Mo, YufengX wrote:
From: Takeshi Yoshimura <t...@jp.ibm.com>
In ppc64le, expanding DMA areas always fail because we cannot
remove
a DMA window. As a result, we cannot allocate more than one memseg
in
ppc64le. This is because vfio_spapr_dma_mem_map() doesn't unmap all
the mapped DMA before removing the window. This patch fixes this
incorrect behavior.
I added a global variable to track current window size since we do
not have better ways to get exact size of it than doing so. sPAPR
IOMMU seems not to provide any ways to get window size with ioctl
interfaces. rte_memseg_walk*() is currently used to calculate
window
size, but it walks memsegs that are marked as used, not mapped. So,
we need to determine if a given memseg is mapped or not, otherwise
the ioctl reports errors due to attempting to unregister memory
addresses that are not registered. The global variable is excluded
in non-ppc64le binaries.
Similar problems happen in user maps. We need to avoid attempting
to
unmap the address that is given as the function's parameter. The
compaction of user maps prevents us from passing correct length for
unmapping DMA at the window recreation. So, I removed it in
ppc64le.
I also fixed the order of ioctl for unregister and unmap. The ioctl
for unregister sometimes report device busy errors due to the
existence of mapped area.
Signed-off-by: Takeshi Yoshimura <t...@jp.ibm.com>
---
OK there are three patches, and two v1's with two different authors
in
reply to the same original patch. There's too much going on here, i
can't review this. Needs splitting.
Also, #ifdef-ing out the map merging seems highly suspect.
With regards to "walking used memsegs, not mapped", unless i'm
misunderstanding something, these are the same - whenever a segment
is
mapped, it is marked as used, and whenever it is unmapped, it is
marked
as free. Could you please explain what is the difference and why is
this
needed?
Is the point of contention here being the fact that whenever the
unmap
callback arrives, the segments still appear used when iterating over
the
map? If that's the case, then i think it would be OK to mark them as
unused *before* triggering callbacks, and chances are some of this
code
wouldn't be needed. That would require a deprecation notice though,
because the API behavior will change (even if this fact is not
documented properly).
--
Thanks,
Anatoly