On 27-Jun-18 5:52 PM, Alejandro Lucero wrote:
On Wed, Jun 27, 2018 at 2:24 PM, Burakov, Anatoly
<anatoly.bura...@intel.com <mailto:anatoly.bura...@intel.com>> wrote:
On 27-Jun-18 11:13 AM, Alejandro Lucero wrote:
On Wed, Jun 27, 2018 at 9:17 AM, Burakov, Anatoly
<anatoly.bura...@intel.com <mailto:anatoly.bura...@intel.com>
<mailto:anatoly.bura...@intel.com
<mailto:anatoly.bura...@intel.com>>> wrote:
On 26-Jun-18 6:37 PM, Alejandro Lucero wrote:
This RFC tries to handle devices with addressing
limitations.
NFP devices
4000/6000 can just handle addresses with 40 bits implying
problems for handling
physical address when machines have more than 1TB of
memory. But
because how
iovas are configured, which can be equivalent to physical
addresses or based on
virtual addresses, this can be a more likely problem.
I tried to solve this some time ago:
https://www.mail-archive.com/dev@dpdk.org/msg45214.html
<https://www.mail-archive.com/dev@dpdk.org/msg45214.html>
<https://www.mail-archive.com/dev@dpdk.org/msg45214.html
<https://www.mail-archive.com/dev@dpdk.org/msg45214.html>>
It was delayed because there was some changes in
progress with
EAL device
handling, and, being honest, I completely forgot about this
until now, when
I have had to work on supporting NFP devices with DPDK and
non-root users.
I was working on a patch for being applied on main DPDK
branch
upstream, but
because changes to memory initialization during the
last months,
this can not
be backported to stable versions, at least the part
where the
hugepages iovas
are checked.
I realize stable versions only allow bug fixing, and this
patchset could
arguably not be considered as so. But without this, it
could be,
although
unlikely, a DPDK used in a machine with more than 1TB,
and then
NFP using
the wrong DMA host addresses.
Although virtual addresses used as iovas are more
dangerous, for
DPDK versions
before 18.05 this is not worse than with physical
addresses,
because iovas,
when physical addresses are not available, are based on a
starting address set
to 0x0.
You might want to look at the following patch:
http://patches.dpdk.org/patch/37149/
<http://patches.dpdk.org/patch/37149/>
<http://patches.dpdk.org/patch/37149/
<http://patches.dpdk.org/patch/37149/>>
Since this patch, IOVA as VA mode uses VA addresses, and
that has
been backported to earlier releases. I don't think there's
any case
where we used zero-based addresses any more.
But memsegs get the iova based on hugepages physaddr, and for VA
mode that is based on 0x0 as starting point.
And as far as I know, memsegs iovas are what end up being used
for IOMMU mappings and what devices will use.
For when physaddrs are available, IOVA as PA mode assigns IOVA
addresses to PA, while IOVA as VA mode assigns IOVA addresses to VA
(both 18.05+ and pre-18.05 as per above patch, which was applied to
pre-18.05 stable releases).
When physaddrs aren't available, IOVA as VA mode assigns IOVA
addresses to VA, both 18.05+ and pre-18.05, as per above patch.
This is right.
If physaddrs aren't available and IOVA as PA mode is used, then i as
far as i can remember, even though technically memsegs get their
addresses set to 0x0 onwards, the actual addresses we get in
memzones etc. are RTE_BAD_IOVA.
This is not right. Not sure if this was the intention, but if PA mode
and physaddrs not available, this code inside vfio_type1_dma_map:
if(rte_eal_iova_mode() == RTE_IOVA_VA)
dma_map.iova = dma_map.vaddr;
else
dma_map.iova = ms[i].iova;
does the IOMMU mapping using the iovas and not the vaddr, with the iovas
starting at 0x0.
Yep, you're right, apologies. I confused this with no-huge option.
--
Thanks,
Anatoly
