Re: [dpdk-dev] [PATCH v3 6/6] DPDK changes for accommodating ENIC PMD

["Sujith Sankar (ssujith)" <ssujith@cisco.com>]

On 24/11/14 10:49 pm, "Neil Horman" <nhorman@tuxdriver.com> wrote:

>On Mon, Nov 24, 2014 at 04:12:48PM +0000, Sujith Sankar (ssujith) wrote:
>> 
>> 
>> On 24/11/14 5:03 pm, "Neil Horman" <nhorman@tuxdriver.com> wrote:
>> 
>> >On Mon, Nov 24, 2014 at 05:45:54AM +0000, Sujith Sankar (ssujith)
>>wrote:
>> >> 
>> >> 
>> >> On 24/11/14 5:47 am, "Neil Horman" <nhorman@tuxdriver.com> wrote:
>> >> 
>> >> >On Sun, Nov 23, 2014 at 09:38:19PM +0530, Sujith Sankar wrote:
>> >> >> Signed-off-by: Sujith Sankar <ssujith@cisco.com>
>> >> >> ---
>> >> >>  config/common_linuxapp                             | 5 +++++
>> >> >>  lib/Makefile                                       | 1 +
>> >> >>  lib/librte_eal/linuxapp/eal/eal_pci_vfio.c         | 7 +++++++
>> >> >>  lib/librte_eal/linuxapp/eal/include/eal_pci_init.h | 1 +
>> >> >>  mk/rte.app.mk                                      | 4 ++++
>> >> >>  5 files changed, 18 insertions(+)
>> >> >> 
>> >> >> diff --git a/config/common_linuxapp b/config/common_linuxapp
>> >> >> index 57b61c9..3c091e7 100644
>> >> >> --- a/config/common_linuxapp
>> >> >> +++ b/config/common_linuxapp
>> >> >> @@ -210,6 +210,11 @@ CONFIG_RTE_LIBRTE_I40E_QUEUE_NUM_PER_VM=4
>> >> >>  CONFIG_RTE_LIBRTE_I40E_ITR_INTERVAL=-1
>> >> >>  
>> >> >>  #
>> >> >> +# Compile burst-oriented Cisco ENIC PMD driver
>> >> >> +#
>> >> >> +CONFIG_RTE_LIBRTE_ENIC_PMD=y
>> >> >> +
>> >> >> +#
>> >> >>  # Compile burst-oriented VIRTIO PMD driver
>> >> >>  #
>> >> >>  CONFIG_RTE_LIBRTE_VIRTIO_PMD=y
>> >> >> diff --git a/lib/Makefile b/lib/Makefile
>> >> >> index e3237ff..1911790 100644
>> >> >> --- a/lib/Makefile
>> >> >> +++ b/lib/Makefile
>> >> >> @@ -43,6 +43,7 @@ DIRS-$(CONFIG_RTE_LIBRTE_CMDLINE) +=
>>librte_cmdline
>> >> >>  DIRS-$(CONFIG_RTE_LIBRTE_ETHER) += librte_ether
>> >> >>  DIRS-$(CONFIG_RTE_LIBRTE_E1000_PMD) += librte_pmd_e1000
>> >> >>  DIRS-$(CONFIG_RTE_LIBRTE_IXGBE_PMD) += librte_pmd_ixgbe
>> >> >> +DIRS-$(CONFIG_RTE_LIBRTE_IXGBE_PMD) += librte_pmd_enic
>> >> >>  DIRS-$(CONFIG_RTE_LIBRTE_I40E_PMD) += librte_pmd_i40e
>> >> >>  DIRS-$(CONFIG_RTE_LIBRTE_PMD_BOND) += librte_pmd_bond
>> >> >>  DIRS-$(CONFIG_RTE_LIBRTE_PMD_RING) += librte_pmd_ring
>> >> >> diff --git a/lib/librte_eal/linuxapp/eal/eal_pci_vfio.c
>> >> >>b/lib/librte_eal/linuxapp/eal/eal_pci_vfio.c
>> >> >> index c776ddc..6bf8f2e 100644
>> >> >> --- a/lib/librte_eal/linuxapp/eal/eal_pci_vfio.c
>> >> >> +++ b/lib/librte_eal/linuxapp/eal/eal_pci_vfio.c
>> >> >> @@ -736,6 +736,7 @@ pci_vfio_map_resource(struct rte_pci_device
>>*dev)
>> >> >>  		maps[i].offset = reg.offset;
>> >> >>  		maps[i].size = reg.size;
>> >> >>  		dev->mem_resource[i].addr = bar_addr;
>> >> >> +		dev->mem_resource[i].len = reg.size;
>> >> >>  	}
>> >> >>  
>> >> >>  	/* if secondary process, do not set up interrupts */
>> >> >> @@ -791,4 +792,10 @@ pci_vfio_is_enabled(void)
>> >> >>  {
>> >> >>  	return vfio_cfg.vfio_enabled;
>> >> >>  }
>> >> >> +
>> >> >> +int
>> >> >> +pci_vfio_container_fd(void)
>> >> >> +{
>> >> >> +	return vfio_cfg.vfio_container_fd;
>> >> >> +}
>> >> >You should move this function definition to a separate patch and
>>put it
>> >> >earlier
>> >> >in the series, as you call this function two patches back.
>> >> 
>> >> Thanks for the comment, Neil.  I shall move this to a separate patch
>>and
>> >> put it earlier in the series.
>> >> 
>> >> >
>> >> >Also, this gives me pause, as it seems like you're working around
>>the
>> >> >VFIO api.
>> >> >From what I see, you just use this to get an fd that you can use in
>>an
>> >> >ioctl to
>> >> >set some DMA settings.  First off, theres already a function called
>> >> >pci_vfio_get_container_fd, which does exactly what you are doing
>>here,
>> >> >with
>> >> >additional safety checking.
>> >> >
>> >> >However, even though there is an existing function to do what you
>> >>want, I
>> >> >would
>> >> >recommend that you not use it for your purposes.  Whenever you
>>expose
>> >> >something
>> >> >like a file descriptor, you run the risk of multiple accessors
>>racing
>> >> >trying to
>> >> >set/unset features and preform operations.  It would be better if
>>you
>> >> >could add
>> >> >apropriate api calls to vfio interface to set what you want.  That
>>way
>> >>the
>> >> >library can add appropriate locking if/when needed
>> >> 
>> >> 
>> >> I see that vfio_cfg.vfio_container_fd is obtained and stored in
>> >> pci_vfio_enable(), and this is not modified later.
>> >> ENIC PMD needs it to add the IOMMU mapping for buffers used for
>> >> communicating with adapter firmware.  That¹s just adding an entry,
>>and
>> >> container fd is just passed as an argument.  So the following
>>addition
>> >>in
>> >> eal_pci_vfio.c should be sufficient.  Since vfio_cfg is per process,
>>I
>> >>do
>> >> not think that any other checking is required.
>> >> 
>> >> int
>> >> pci_vfio_map_dma(struct vfio_iommu_type1_dma_map *dma_map)
>> >> {
>> >> 	return ioctl(vfio_cfg.vfio_container_fd, VFIO_IOMMU_MAP_DMA,
>>dma_map);
>> >> }
>> >> 
>> >> 
>> >> 
>> >> Does this look alright?  Do you think that I¹ve missed out anything
>> >>here?
>> >> 
>> >It looks better yes, but I'm still confused as to why its necessecary.
>> >Looking
>> >back at your use of the fd, you're adding an iov entry for a buffer
>> >allocated
>> >via rte_memzone_reserve, which should come out of the dpdk's configured
>> >memory.
>> >In pci_vfio_setup_dma_maps, which is part of the pci probe path in eal
>> >library,
>> >all of the DPDK's physically available memory is already mapped into
>>the
>> >iommu
>> >in a 1:1 fashion.  So why do you need to do this again?
>> 
>> Yes, ideally all the memory allocated using
>>rte_memzone_reserve_aligned()
>> should have its mapping already there in IOMMU.  The code that adds the
>> mapping was not there initially, but while testing, I saw that it was
>> giving DMAR errors (like what’s shown below).  Putting it back solved
>>the
>> problem.
>> 
>> 
>> [295042.852620] DMAR:[fault reason 05] PTE Write access is not set
>> [295044.406282] dmar: DRHD: handling fault status reg 602
>> [295044.467981] dmar: DMAR:[DMA Write] Request device [86:00.0] fault
>>addr
>> 7fbd73b32000
>> 
>Ok, so what I hear you saying is that, now that that mapping code is
>available
>in the pci probe path, you can remove your workaround correct?

Comparing the two mapping functions, I could find out a difference.  ENIC
PMD is using virtual address of the buffers to fill dma_map->iova, while
the lib is filling in the phys_addr.  Both the cases work.
I’ve modified ENIC PMD to use phys_addr and the initial tests went through
fine.  Let me spend some more time testing it.  After that I shall get
back with V4.

Thank you Neil !

-Sujith

>
>Neil
>
>> 
>> Regards,
>> -Sujith
>> 
>> >
>> >Neil
>> >
>>