Re: [dpdk-dev] [PATCH dpdk 5/5] RFC: vfio/ppc64/spapr: Use correct bus addresses for DMA map

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 21/04/17 05:16, gowrishankar muthukrishnan wrote:
> On Thursday 20 April 2017 07:52 PM, Alexey Kardashevskiy wrote:
>> On 20/04/17 23:25, Alexey Kardashevskiy wrote:
>>> On 20/04/17 19:04, Jonas Pfefferle1 wrote:
>>>> Alexey Kardashevskiy <aik@ozlabs.ru> wrote on 20/04/2017 09:24:02:
>>>>
>>>>> From: Alexey Kardashevskiy <aik@ozlabs.ru>
>>>>> To: dev@dpdk.org
>>>>> Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, JPF@zurich.ibm.com,
>>>>> Gowrishankar Muthukrishnan <gowrishankar.m@in.ibm.com>
>>>>> Date: 20/04/2017 09:24
>>>>> Subject: [PATCH dpdk 5/5] RFC: vfio/ppc64/spapr: Use correct bus
>>>>> addresses for DMA map
>>>>>
>>>>> VFIO_IOMMU_SPAPR_TCE_CREATE ioctl() returns the actual bus address for
>>>>> just created DMA window. It happens to start from zero because the
>>>>> default
>>>>> window is removed (leaving no windows) and new window starts from zero.
>>>>> However this is not guaranteed and the new window may start from another
>>>>> address, this adds an error check.
>>>>>
>>>>> Another issue is that IOVA passed to VFIO_IOMMU_MAP_DMA should be a PCI
>>>>> bus address while in this case a physical address of a user page is used.
>>>>> This changes IOVA to start from zero in a hope that the rest of DPDK
>>>>> expects this.
>>>> This is not the case. DPDK expects a 1:1 mapping PA==IOVA. It will use the
>>>> phys_addr of the memory segment it got from /proc/self/pagemap cf.
>>>> librte_eal/linuxapp/eal/eal_memory.c. We could try setting it here to the
>>>> actual iova which basically makes the whole virtual to phyiscal mapping
>>>> with pagemap unnecessary which I believe should be the case for VFIO
>>>> anyway. Pagemap should only be needed when using pci_uio.
>>>
>>> Ah, ok, makes sense now. But it sure needs a big fat comment there as it is
>>> not obvious why host RAM address is used there as DMA window start is not
>>> guaranteed.
>> Well, either way there is some bug - ms[i].phys_addr and ms[i].addr_64 both
>> have exact same value, in my setup it is 3fffb33c0000 which is a userspace
>> address - at least ms[i].phys_addr must be physical address.
> 
> This patch breaks i40e_dev_init() in my server.
> 
> EAL: PCI device 0004:01:00.0 on NUMA socket 1
> EAL:   probe driver: 8086:1583 net_i40e
> EAL:   using IOMMU type 7 (sPAPR)
> eth_i40e_dev_init(): Failed to init adminq: -32
> EAL: Releasing pci mapped resource for 0004:01:00.0
> EAL: Calling pci_unmap_resource for 0004:01:00.0 at 0x3fff82aa0000
> EAL: Requested device 0004:01:00.0 cannot be used
> EAL: PCI device 0004:01:00.1 on NUMA socket 1
> EAL:   probe driver: 8086:1583 net_i40e
> EAL:   using IOMMU type 7 (sPAPR)
> eth_i40e_dev_init(): Failed to init adminq: -32
> EAL: Releasing pci mapped resource for 0004:01:00.1
> EAL: Calling pci_unmap_resource for 0004:01:00.1 at 0x3fff82aa0000
> EAL: Requested device 0004:01:00.1 cannot be used
> EAL: No probed ethernet devices
> 
> I have two memseg each of 1G size. Their mapped PA and VA are also different.
> 
> (gdb) p /x ms[0]
> $3 = {phys_addr = 0x1e0b000000, {addr = 0x3effaf000000, addr_64 =
> 0x3effaf000000},
>   len = 0x40000000, hugepage_sz = 0x1000000, socket_id = 0x1, nchannel =
> 0x0, nrank = 0x0}
> (gdb) p /x ms[1]
> $4 = {phys_addr = 0xf6d000000, {addr = 0x3efbaf000000, addr_64 =
> 0x3efbaf000000},
>   len = 0x40000000, hugepage_sz = 0x1000000, socket_id = 0x0, nchannel =
> 0x0, nrank = 0x0}
> 
> Could you please recheck this. May be, if new DMA window does not start
> from bus address 0,
> only then you reset dma_map.iova for this offset ?

As we figured out, it is --no-huge effect.

Another thing - as I read the code - the window size comes from
rte_eal_get_physmem_size(). On my 512GB machine, DPDK allocates only 16GB
window so it is far away from 1:1 mapping which is believed to be DPDK
expectation. Looking now for a better version of rte_eal_get_physmem_size()...


And another problem - after few unsuccessful starts of app/testpmd, all
huge pages are gone:

aik@stratton2:~$ cat /proc/meminfo
MemTotal:       535527296 kB
MemFree:        516662272 kB
MemAvailable:   515501696 kB
...
HugePages_Total:    1024
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:      16384 kB


How is that possible? What is pinning these pages so testpmd process exit
does not clear that up?




> 
> 
> Thanks,
> Gowrishankar
> 
>>
>>>
>>>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>>>> ---
>>>>>   lib/librte_eal/linuxapp/eal/eal_vfio.c | 12 ++++++++++--
>>>>>   1 file changed, 10 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/lib/librte_eal/linuxapp/eal/eal_vfio.c b/lib/
>>>>> librte_eal/linuxapp/eal/eal_vfio.c
>>>>> index 46f951f4d..8b8e75c4f 100644
>>>>> --- a/lib/librte_eal/linuxapp/eal/eal_vfio.c
>>>>> +++ b/lib/librte_eal/linuxapp/eal/eal_vfio.c
>>>>> @@ -658,7 +658,7 @@ vfio_spapr_dma_map(int vfio_container_fd)
>>>>>   {
>>>>>      const struct rte_memseg *ms = rte_eal_get_physmem_layout();
>>>>>      int i, ret;
>>>>> -
>>>>> +   phys_addr_t io_offset;
>>>>>      struct vfio_iommu_spapr_register_memory reg = {
>>>>>         .argsz = sizeof(reg),
>>>>>         .flags = 0
>>>>> @@ -702,6 +702,13 @@ vfio_spapr_dma_map(int vfio_container_fd)
>>>>>         return -1;
>>>>>      }
>>>>>   +   io_offset = create.start_addr;
>>>>> +   if (io_offset) {
>>>>> +      RTE_LOG(ERR, EAL, "  DMA offsets other than zero is not
>>>>> supported, "
>>>>> +            "new window is created at %lx\n", io_offset);
>>>>> +      return -1;
>>>>> +   }
>>>>> +
>>>>>      /* map all DPDK segments for DMA. use 1:1 PA to IOVA mapping */
>>>>>      for (i = 0; i < RTE_MAX_MEMSEG; i++) {
>>>>>         struct vfio_iommu_type1_dma_map dma_map;
>>>>> @@ -723,7 +730,7 @@ vfio_spapr_dma_map(int vfio_container_fd)
>>>>>         dma_map.argsz = sizeof(struct vfio_iommu_type1_dma_map);
>>>>>         dma_map.vaddr = ms[i].addr_64;
>>>>>         dma_map.size = ms[i].len;
>>>>> -      dma_map.iova = ms[i].phys_addr;
>>>>> +      dma_map.iova = io_offset;
>>>>>         dma_map.flags = VFIO_DMA_MAP_FLAG_READ |
>>>>>                VFIO_DMA_MAP_FLAG_WRITE;
>>>>>   @@ -735,6 +742,7 @@ vfio_spapr_dma_map(int vfio_container_fd)
>>>>>            return -1;
>>>>>         }
>>>>>   +      io_offset += dma_map.size;
>>>>>      }
>>>>>        return 0;
>>>>> -- 
>>>>> 2.11.0
>>>>>
>>>
>>
> 
> 


-- 
Alexey