On Wed, Jun 27, 2018 at 9:17 AM, Burakov, Anatoly <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 >> >> 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/ > > 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. > > 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 >
