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>> 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>
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/>
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.
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.
Since 18.05, those iovas can, and usually are, higher than 1TB, as
they
are based on 64 bits address space addresses, and by default the
kernel uses a
starting point far higher than 1TB.
This patchset applies to stable 17.11.3 but I will be happy to
submit patches, if
required, for other DPDK stable versions.
--
Thanks,
Anatoly
--
Thanks,
Anatoly
