[dpdk-dev] [PATCH 5/7] mem: modify error message for DMA mask check
Alejandro Lucero
alejandro.lucero at netronome.com
Thu Nov 1 12:32:48 CET 2018
On Thu, Nov 1, 2018 at 11:12 AM Burakov, Anatoly <anatoly.burakov at intel.com>
wrote:
> On 01-Nov-18 11:03 AM, Alejandro Lucero wrote:
> >
> >
> > On Thu, Nov 1, 2018 at 10:29 AM Burakov, Anatoly
> > <anatoly.burakov at intel.com <mailto:anatoly.burakov at intel.com>> wrote:
> >
> > On 31-Oct-18 5:29 PM, Alejandro Lucero wrote:
> > > If DMA mask checks shows mapped memory out of the supported range
> > > specified by the DMA mask, nothing can be done but return an error
> > > an report the error. This can imply the app not being executed at
> > > all or precluding dynamic memory allocation once the app is
> running.
> > > In any case, we can advice the user to force IOVA as PA if
> currently
> > > IOVA being VA and user being root.
> > >
> > > Signed-off-by: Alejandro Lucero <alejandro.lucero at netronome.com
> > <mailto:alejandro.lucero at netronome.com>>
> > > ---
> >
> > General comment - legacy memory will also need this check, correct?
> >
> >
> > Yes, there is another patch adding this for both, legacy-mem and no-huge
> > options.
> >
> > > lib/librte_eal/common/malloc_heap.c | 35
> > +++++++++++++++++++++++++----
> > > 1 file changed, 31 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/lib/librte_eal/common/malloc_heap.c
> > b/lib/librte_eal/common/malloc_heap.c
> > > index 7d423089d..711622f19 100644
> > > --- a/lib/librte_eal/common/malloc_heap.c
> > > +++ b/lib/librte_eal/common/malloc_heap.c
> > > @@ -5,8 +5,10 @@
> > > #include <stddef.h>
> > > #include <stdlib.h>
> > > #include <stdio.h>
> > > +#include <unistd.h>
> > > #include <stdarg.h>
> > > #include <errno.h>
> > > +#include <sys/types.h>
> > > #include <sys/queue.h>
> > >
> > > #include <rte_memory.h>
> > > @@ -294,7 +296,6 @@ alloc_pages_on_heap(struct malloc_heap *heap,
> > uint64_t pg_sz, size_t elt_size,
> > > size_t alloc_sz;
> > > int allocd_pages;
> > > void *ret, *map_addr;
> > > - uint64_t mask;
> > >
> > > alloc_sz = (size_t)pg_sz * n_segs;
> > >
> > > @@ -322,11 +323,37 @@ alloc_pages_on_heap(struct malloc_heap
> > *heap, uint64_t pg_sz, size_t elt_size,
> > > goto fail;
> > > }
> > >
> > > + /* Once we have all the memseg lists configured, if there
> > is a dma mask
> > > + * set, check iova addresses are not out of range.
> > Otherwise the device
> > > + * setting the dma mask could have problems with the mapped
> > memory.
> > > + *
> > > + * There are two situations when this can happen:
> > > + * 1) memory initialization
> > > + * 2) dynamic memory allocation
> > > + *
> > > + * For 1), an error when checking dma mask implies app can
> > not be
> > > + * executed. For 2) implies the new memory can not be added.
> > > + */
> > > if (mcfg->dma_maskbits) {
> > > if (rte_mem_check_dma_mask(mcfg->dma_maskbits)) {
> > > - RTE_LOG(ERR, EAL,
> > > - "%s(): couldn't allocate memory due
> > to DMA mask\n",
> > > - __func__);
> > > + /* Currently this can only happen if IOMMU
> > is enabled
> > > + * with RTE_ARCH_X86. It is not safe to use
> > this memory
> > > + * so returning an error here.
> >
> > I don't think it's RTE_ARCH_X86-only. It can be any other arch with
> an
> > IOMMU that's reporting addressing limitations.
> >
> >
> > Right, but it is just IOMMU hardware from this architecture having the
> > current limitation.
> > I was trying to just explain why this can happen but I can remove the
> > reference to specific
> > architecture problems.
> >
> >
> > > + *
> > > + * If IOVA is VA, advice to try with
> > '--iova-mode pa'
> > > + * which could solve some situations when
> > IOVA VA is not
> > > + * really needed.
> > > + */
> > > + uid_t user = getuid();
> > > + if ((rte_eal_iova_mode() == RTE_IOVA_VA) &&
> > user == 0)
> >
> > rte_eal_using_phys_addrs()?
> >
> > (the above function name is a bit of a misnomer, it really checks if
> > they are available, but not necessarily used - it will return true in
> > RTE_IOVA_VA mode if you're running as root)
> >
> >
> > rte_eal_iova_mode returns rte_eal_get_configuration()->iova_mode what
> > is set during initialization. It can be PA not just because IOMMU (not
> > after the patch)
> > but because some PMD does not reports IOVA VA support or because UIO is
> > in use.
> > Checking for root is because IOVA PA can not be used if non root.
>
> You've misinterpreted my comment.
>
> rte_eal_using_phys_addrs() will effectively return true if you're
> running as root. There's no need for an uid check.
>
> Ok. I got it now, and it is definitely better than adding the uid check.
Thanks
> The "misnomer" comment was about the rte_eal_using_phys_addrs() - it
> reads like it would return false in IOVA_VA mode, but in reality, it
> will return true even if IOVA_VA mode - it really should be named
> "rte_eal_phys_addrs_available()" rather than
> "rte_eal_using_phys_addrs()". This would make it clearer.
>
> >
> >
> > > + RTE_LOG(ERR, EAL,
> > > + "%s(): couldn't allocate
> > memory due to DMA mask.\n"
> > > + "Try with 'iova-mode=pa'\n",
> > > + __func__);
> > > + else
> > > + RTE_LOG(ERR, EAL,
> > > + "%s(): couldn't allocate
> > memory due to DMA mask\n",
> > > + __func__);
> >
> > I don't think the error message is terribly descriptive. Looking at
> it
> > through the eyes of someone who sees it for the first time and who
> has
> > no idea what "iova-mode=pa" is, i think it would be more useful to
> word
> > it the following way:
> >
> > couldn't allocate memory due to IOVA exceeding limits of current DMA
> > mask.
> > [for non-using phys addrs case] Please try initializing EAL with
> > --iova-mode=pa parameter.
> >
> >
> > I'm happy with using your terrific description instead ;-)
> > Thanks!
> >
> > Also, generally newlines in RTE_LOG look ugly unless you indent the
> > line :)
> >
> > > goto fail;
> > > }
> > > }
> > >
> >
> >
> > --
> > Thanks,
> > Anatoly
> >
>
>
> --
> Thanks,
> Anatoly
>
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