Re: [PATCH] eal: don't advertise a physical address when no hugepages

[Olivier Matz <olivier.matz@6wind.com>]

Hi Jan,

On Sat, 10 Jun 2017 10:31:22 +0200, Jan Blunck <jblunck@infradead.org> wrote:
> On Fri, Jun 9, 2017 at 10:29 AM, Olivier Matz <olivier.matz@6wind.com> wrote:
> > When populating a mempool with a virtual memory area, the mempool
> > library expects to be able to get the physical address of each page.
> >
> > When started with --no-huge, the physical addresses may not be available
> > because the pages are not locked in memory. It sometimes returns
> > RTE_BAD_PHYS_ADDR, which makes the mempool_populate() function to fail.
> >
> > This was working before the commit cdc242f260e7 ("eal/linux: support
> > running as unprivileged user"), because rte_mem_virt2phy() was returning
> > 0 instead of RTE_BAD_PHYS_ADDR, which was seen as a valid physical
> > address.
> >
> > Since --no-huge is a debug function that breaks the support of physical
> > drivers, always set physical addresses to RTE_BAD_PHYS_ADDR in memzones
> > or in rte_mem_virt2phy(), and ensure that mempool won't complain in that
> > case.
> >
> > Fixes: cdc242f260e7 ("eal/linux: support running as unprivileged user")
> >
> > CC: stable@dpdk.org
> > Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> > ---
> >  lib/librte_eal/common/eal_common_memzone.c | 5 ++++-
> >  lib/librte_eal/linuxapp/eal/eal_memory.c   | 7 +++++++
> >  lib/librte_mempool/rte_mempool.c           | 2 +-
> >  3 files changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/librte_eal/common/eal_common_memzone.c b/lib/librte_eal/common/eal_common_memzone.c
> > index 3026e36b8..c465c8fc2 100644
> > --- a/lib/librte_eal/common/eal_common_memzone.c
> > +++ b/lib/librte_eal/common/eal_common_memzone.c
> > @@ -251,7 +251,10 @@ memzone_reserve_aligned_thread_unsafe(const char *name, size_t len,
> >
> >         mcfg->memzone_cnt++;
> >         snprintf(mz->name, sizeof(mz->name), "%s", name);
> > -       mz->phys_addr = rte_malloc_virt2phy(mz_addr);
> > +       if (rte_eal_has_hugepages())
> > +               mz->phys_addr = rte_malloc_virt2phy(mz_addr);
> > +       else
> > +               mz->phys_addr = RTE_BAD_PHYS_ADDR;  
> 
> Since you set phys_addrs_available to false rte_malloc_virt2phy()
> anyway returns RTE_BAD_PHYS_ADDR so I believe the conditional isn't
> necessary here.
> 
> Rest of the patch looks good to me.

The variable phys_addrs_available only impacts rte_mem_virt2phy().
Here, for memzones allocation, rte_malloc_virt2phy() is used, and
it gets its physical address by retrieving it from the memseg structure.

With the full patch, "dump_memzone" displays something like:
  Zone 0: name:<rte_eth_dev_data>, phys:0xffffffffffffffff, len:0x30100, [...]
  ...

If I strip the memzone part, it displays:
  Zone 0: name:<rte_eth_dev_data>, phys:0x7fe382c62640, len:0x30100, [...]
  ...

So I think we should either keep the patch as is, or change the memseg
and malloc part like this (it's maybe better):

  --- a/lib/librte_eal/common/rte_malloc.c
  +++ b/lib/librte_eal/common/rte_malloc.c
  @@ -254,5 +254,7 @@ rte_malloc_virt2phy(const void *addr)
          const struct malloc_elem *elem = malloc_elem_from_data(addr);
          if (elem == NULL)
                  return 0;
  +       if (elem->ms->phys_addr == RTE_BAD_PHYS_ADDR)
  +               return RTE_BAD_PHYS_ADDR;
          return elem->ms->phys_addr + ((uintptr_t)addr - (uintptr_t)elem->ms->addr);
   }
  diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
  index 1c99852..2a401ca 100644
  --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
  +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
  @@ -973,7 +973,7 @@ rte_eal_hugepage_init(void)
                                          strerror(errno));
                          return -1;
                  }
  -               mcfg->memseg[0].phys_addr = (phys_addr_t)(uintptr_t)addr;
  +               mcfg->memseg[0].phys_addr = RTE_BAD_PHYS_ADDR;
                  mcfg->memseg[0].addr = addr;
                  mcfg->memseg[0].hugepage_sz = RTE_PGSIZE_4K;
                  mcfg->memseg[0].len = internal_config.memory;


Let me know what you are ok with this and I'll send a v2.

Thanks,
Olivier