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

[Jan Blunck <jblunck@infradead.org>]

On Fri, Jun 23, 2017 at 10:11 AM, Olivier Matz <olivier.matz@6wind.com> wrote:
> 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.
>

This approach looks better to me.

Thanks,
Jan