Re: [dpdk-dev] [PATCH v3 1/3] eal/linux: select iova-mode va with no-huge option

[Jerin Jacob <jerinjacobk@gmail.com>]

On Mon, Mar 23, 2020 at 11:11 PM dwilder <dwilder@us.ibm.com> wrote:
>
> Thanks you for your review Jerin.  See my responses are inline.
>
> On 2020-03-20 06:24, Jerin Jacob wrote:
> > On Fri, Feb 21, 2020 at 4:22 AM David Wilder <dwilder@us.ibm.com>
> > wrote:
> >>
> >> If --no-huge is set and iova-mode has not been specified force VA
> >> mode.
> >> If --no-huge and --iova-mode=PA is requested error out as this is
> >> an impossible configuration.
> >>
> >> Signed-off-by: David Wilder <dwilder@us.ibm.com>
> >> ---
> >>  lib/librte_eal/linux/eal/eal.c | 14 ++++++++++++++
> >>  1 file changed, 14 insertions(+)
> >>
> >> diff --git a/lib/librte_eal/linux/eal/eal.c
> >> b/lib/librte_eal/linux/eal/eal.c
> >> index 9530ee55f..d3a0a1731 100644
> >> --- a/lib/librte_eal/linux/eal/eal.c
> >> +++ b/lib/librte_eal/linux/eal/eal.c
> >> @@ -1062,9 +1062,16 @@ rte_eal_init(int argc, char **argv)
> >>
> >>         /* if no EAL option "--iova-mode=<pa|va>", use bus IOVA scheme
> >> */
> >>         if (internal_config.iova_mode == RTE_IOVA_DC) {
> >> +
> >>                 /* autodetect the IOVA mapping mode */
> >>                 enum rte_iova_mode iova_mode =
> >> rte_bus_get_iommu_class();
> >>
> >> +               if (iova_mode == RTE_IOVA_PA &&
> >> !rte_eal_has_hugepages()) {
> >> +                       iova_mode = RTE_IOVA_VA;
>
> >
> > What if igb_uio or vfio_nommu has been loaded(i.e no iommu support
> > enabled from the driver)? This would fail.
>
> Yes they would fail.  If igb_uio or vfio_nommu (or any driver) cant be
> forced to VA mode it cant be used with out hugepages.  Drivers can be
> available but not used therefor we print a warning message.

I think, the warning will not be enough as the system will fail anyway.

iova_mode == RTE_IOVA_PA && rte_eal_has_hugepages() == 0 && no_iommu == 1
case, we need to return error.

iova_mode == RTE_IOVA_PA && rte_eal_has_hugepages() == 0 && no_iommu == 0
case warning is enough.

>
> >
> >> +                       RTE_LOG(WARNING, EAL, "Some buses want 'PA'
> >> but forcing 'VA' because --no-huge is requested.\n");
> >> +                       RTE_LOG(WARNING, EAL, "Not all buses may be
> >> able to initialize.\n");
> >> +               }
> >> +
> >>                 if (iova_mode == RTE_IOVA_DC) {
> >>                         RTE_LOG(DEBUG, EAL, "Buses did not request a
> >> specific IOVA mode.\n");
> >>
> >> @@ -1111,6 +1118,13 @@ rte_eal_init(int argc, char **argv)
> >>                         internal_config.iova_mode;
> >>         }
> >>
> >> +       if (rte_eal_iova_mode() == RTE_IOVA_PA &&
> >> +           rte_eal_has_hugepages() == 0) {
> >> +               rte_eal_init_alert("Cannot use IOVA as 'PA' with
> >> --no-huge");
> >
> > Top of the tree already detecting this case. am I missing anything?
> >
> > [master]dell[dpdk.org] $ sudo ./build/app/test/dpdk-test  -c 0x3
> > --no-huge --iova-mode=pa
> > EAL: Detected 56 lcore(s)
> > EAL: Detected 2 NUMA nodes
> > EAL: Static memory layout is selected, amount of reserved memory can
> > be adjusted with -m or --socket-mem
> > EAL: Multi-process socket /var/run/dpdk/rte/mp_socket
> > EAL: FATAL: Cannot use IOVA as 'PA' since physical addresses are not
> > available
> > EAL: Cannot use IOVA as 'PA' since physical addresses are not available
> >
>
> The check you reference is reporting that physical address are not
> available, for example no permissions to read /proc/self/pagemap.  In
> this case, if --no-huge is set then PA mode is not allowed. There is no
> guarantee that physical address are persistent with out using hugepages.

Since this check is under the following, Yes, make sense for the check.
The old command has explicit  --iova-mode=pa. So it is in the
different code paths.

/* if no EAL option "--iova-mode=<pa|va>", use bus IOVA scheme */
        if (internal_config.iova_mode == RTE_IOVA_DC) {

>
>
> >> +               rte_errno = EINVAL;
> >> +               return -1;
> >> +       }
> >> +
> >>         if (rte_eal_iova_mode() == RTE_IOVA_PA && !phys_addrs) {
> >>                 rte_eal_init_alert("Cannot use IOVA as 'PA' since
> >> physical addresses are not available");
> >>                 rte_errno = EINVAL;
> >> --
> >> 2.25.0
> >>