On Thu, Feb 8, 2018 at 3:20 AM, Burakov, Anatoly <anatoly.bura...@intel.com> wrote:
> On 06-Feb-18 5:55 PM, Ravi Kerur wrote: > >> >> Hi Anatoly, >> >> I am actually confused with the state of vIOMMU + DPDK. Can you please >> help me clarify? >> >> I tested following DPDK versions >> >> (1) DPDK 17.11, exhibits the issue (IOMMU width as reported by RedHat and >> solution is to prevent using the patch) >> (2) DPDK 17.05.02 (stable release) using 'testpmd' I was able to bind a >> device in VM with VFIO driver and no DMAR error message on host >> (3) DPDK 16.11.02 (stable release) using 'testpmd' I was able to bind a >> device in VM with VFIO driver and no DMAR error message on host >> >> Clearly issue seen in 17.11 without the patch you mentioned is a >> regression or the issue was masked in earlier DPDK version? I did not test >> traffic with any DPDK version because I wanted to first get DMAR errors on >> host gone. >> >> Our application 'v1' is integrated with DPDK 16.11 and 'v2' is integrated >> with DPDK 17.05.01. In both 'v1' and 'v2' cases I don't see IOMMU width >> error messages on VM, however, DMAR error messages are seen host. I am not >> able to relate what causes DMAR error messages on host? >> >> >> Thanks. >> >> > Hi Ravi, > > vIOMMU support is out of our hands, really - we can only make use of > hardware (or emulation of it) that is available. 39-bit wide address *can* > work, you just have to be lucky and get PA addresses that would fit into 39 > bits (so under 512G limit), because we set up IOVA addresses to be 1:1 to > physical addresses. We could, in principle, set up IOVA addresses to go > from zero instead of them being a 1:1 mapping to physical addresses, but > that would introduce need to translate addresses between IOVA and physical > in some cases (e.g. KNI). > > I'm not aware of any changes between 16.11 and 17.11 (and indeed 18.02) > that would make or break support for 39-bit wide PA addresses for IOMMU. It > is possible that VF/PF drivers do something differently which results in > DMAR errors showing up sooner rather than later, but as far as VFIO support > itself is concerned, there were no major changes in those releases. > > Hi Anatoly, Thank you for your explanation. I would like to ask one more thing as I need to get v-iommu+ dpdk working in VM. Can you please tell me what determines 'Host Address Width", I know my question has nothing to do with dpdk and this is a dpdk list, but if you have any information please share it? I googled and found couple of ways to influence 'Host Address Width = 46' in guest as well (since dpdk + iommu works fine on host and DMAR on host reports address width as 46). (1) Qemu has CPU param 'host-phys-bits' boolean, when set to true copies it from host (2) Qemu has 'phys-bits' integer, when set to '46' should influence guest Using above options when instantiating a VM doesn't help, Guest VM still ends up with 'Host address width = 39'. (3) There is another Qemu option 'x-aw-bits' which is for VT-d which can be set to '39' or '48'. This doesn't help either. Thanks. -- > Thanks, > Anatoly >
