Re: [dpdk-dev] [PATCH 18.11 v2] pci/vfio: allow mapping MSI-X BARs if kernel allows it

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 02-Aug-18 7:47 AM, Takeshi Yoshimura wrote:
> 2018-07-31 20:28 GMT+09:00 Anatoly Burakov <anatoly.burakov@intel.com>:
>> Currently, DPDK will skip mapping some areas (or even an entire BAR)
>> if MSI-X table happens to be in them but is smaller than page size.
>>
>> Kernels 4.16+ will allow mapping MSI-X BARs [1], and will report this
>> as a capability flag. Capability flags themselves are also only
>> supported since kernel 4.6 [2].
>>
>> This commit will introduce support for checking VFIO capabilities,
>> and will use it to check if we are allowed to map BARs with MSI-X
>> tables in them, along with backwards compatibility for older
>> kernels, including a workaround for a variable rename in VFIO
>> region info structure [3].
>>
>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/
>> linux.git/commit/?id=a32295c612c57990d17fb0f41e7134394b2f35f6
>>
>> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/
>> linux.git/commit/?id=c84982adb23bcf3b99b79ca33527cd2625fbe279
>>
>> [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/
>> linux.git/commit/?id=ff63eb638d63b95e489f976428f1df01391e15e4
>>
>> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
>> ---
>>
>> Notes:
>>      v2->v1:
>>      - Fix pointer in pci_vfio_get_region_info
>>      - Fix commit message
>>
>>   drivers/bus/pci/linux/pci_vfio.c         | 127 ++++++++++++++++++++---
>>   lib/librte_eal/common/include/rte_vfio.h |  26 +++++
>>   2 files changed, 140 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/bus/pci/linux/pci_vfio.c b/drivers/bus/pci/linux/pci_vfio.c
>> index 686386d6a..24f665c20 100644
>> --- a/drivers/bus/pci/linux/pci_vfio.c
>> +++ b/drivers/bus/pci/linux/pci_vfio.c
>> @@ -415,6 +415,88 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
>>          return 0;
>>   }
>>
>> +/*
>> + * region info may contain capability headers, so we need to keep reallocating
>> + * the memory until we match allocated memory size with argsz.
>> + */
>> +static int
>> +pci_vfio_get_region_info(int vfio_dev_fd, struct vfio_region_info **info,
>> +               int region)
>> +{
>> +       struct vfio_region_info *ri;
>> +       size_t argsz = sizeof(*ri);
>> +       int ret;
>> +
>> +       ri = malloc(sizeof(*ri));
>> +       if (ri == NULL) {
>> +               RTE_LOG(ERR, EAL, "Cannot allocate memory for region info\n");
>> +               return -1;
>> +       }
>> +again:
>> +       memset(ri, 0, argsz);
>> +       ri->argsz = argsz;
>> +       ri->index = region;
>> +
>> +       ret = ioctl(vfio_dev_fd, VFIO_DEVICE_GET_REGION_INFO, ri);
>> +       if (ret) {
>> +               free(ri);
>> +               return ret;
>> +       }
>> +       if (ri->argsz != argsz) {
>> +               argsz = ri->argsz;
>> +               ri = realloc(ri, argsz);
>> +
>> +               if (ri == NULL) {
>> +                       RTE_LOG(ERR, EAL, "Cannot reallocate memory for region info\n");
>> +                       return -1;
>> +               }
>> +               goto again;
>> +       }
>> +       *info = ri;
>> +
>> +       return 0;
>> +}
>> +
>> +static struct vfio_info_cap_header *
>> +pci_vfio_info_cap(struct vfio_region_info *info, int cap)
>> +{
>> +       struct vfio_info_cap_header *h;
>> +       size_t offset;
>> +
>> +       if ((info->flags & RTE_VFIO_INFO_FLAG_CAPS) == 0) {
>> +               /* VFIO info does not advertise capabilities */
>> +               return NULL;
>> +       }
>> +
>> +       offset = VFIO_CAP_OFFSET(info);
>> +       while (offset != 0) {
>> +               h = RTE_PTR_ADD(info, offset);
>> +               if (h->id == cap)
>> +                       return h;
>> +               offset = h->next;
>> +       }
>> +       return NULL;
>> +}
>> +
>> +static int
>> +pci_vfio_msix_is_mappable(int vfio_dev_fd, int msix_region)
>> +{
>> +       struct vfio_region_info *info;
>> +       int ret;
>> +
>> +       ret = pci_vfio_get_region_info(vfio_dev_fd, &info, msix_region);
>> +       if (ret < 0)
>> +               return -1;
>> +
>> +       ret = pci_vfio_info_cap(info, RTE_VFIO_CAP_MSIX_MAPPABLE) != NULL;
>> +
>> +       /* cleanup */
>> +       free(info);
>> +
>> +       return ret;
>> +}
>> +
>> +
>>   static int
>>   pci_vfio_map_resource_primary(struct rte_pci_device *dev)
>>   {
>> @@ -464,56 +546,75 @@ pci_vfio_map_resource_primary(struct rte_pci_device *dev)
>>          if (ret < 0) {
>>                  RTE_LOG(ERR, EAL, "  %s cannot get MSI-X BAR number!\n",
>>                                  pci_addr);
>> -               goto err_vfio_dev_fd;
>> +               goto err_vfio_res;
>> +       }
>> +       /* if we found our MSI-X BAR region, check if we can mmap it */
>> +       if (vfio_res->msix_table.bar_index != -1) {
>> +               int ret = pci_vfio_msix_is_mappable(vfio_dev_fd,
>> +                               vfio_res->msix_table.bar_index);
>> +               if (ret < 0) {
>> +                       RTE_LOG(ERR, EAL, "Couldn't check if MSI-X BAR is mappable\n");
>> +                       goto err_vfio_res;
>> +               } else if (ret != 0) {
>> +                       /* we can map it, so we don't care where it is */
>> +                       RTE_LOG(DEBUG, EAL, "VFIO reports MSI-X BAR as mappable\n");
>> +                       vfio_res->msix_table.bar_index = -1;
>> +               }
>>          }
>>
>>          for (i = 0; i < (int) vfio_res->nb_maps; i++) {
>> -               struct vfio_region_info reg = { .argsz = sizeof(reg) };
>> +               struct vfio_region_info *reg;
>>                  void *bar_addr;
>>
>> -               reg.index = i;
>> -
>> -               ret = ioctl(vfio_dev_fd, VFIO_DEVICE_GET_REGION_INFO, &reg);
>> -               if (ret) {
>> +               ret = pci_vfio_get_region_info(vfio_dev_fd, &reg, i);
>> +               if (ret < 0) {
>>                          RTE_LOG(ERR, EAL, "  %s cannot get device region info "
>> -                                       "error %i (%s)\n", pci_addr, errno, strerror(errno));
>> +                               "error %i (%s)\n", pci_addr, errno,
>> +                               strerror(errno));
>>                          goto err_vfio_res;
>>                  }
>>
>>                  /* chk for io port region */
>>                  ret = pci_vfio_is_ioport_bar(vfio_dev_fd, i);
>> -               if (ret < 0)
>> +               if (ret < 0) {
>> +                       free(reg);
>>                          goto err_vfio_res;
>> -               else if (ret) {
>> +               } else if (ret) {
>>                          RTE_LOG(INFO, EAL, "Ignore mapping IO port bar(%d)\n",
>>                                          i);
>> +                       free(reg);
>>                          continue;
>>                  }
>>
>>                  /* skip non-mmapable BARs */
>> -               if ((reg.flags & VFIO_REGION_INFO_FLAG_MMAP) == 0)
>> +               if ((reg->flags & VFIO_REGION_INFO_FLAG_MMAP) == 0) {
>> +                       free(reg);
>>                          continue;
>> +               }
>>
>>                  /* try mapping somewhere close to the end of hugepages */
>>                  if (pci_map_addr == NULL)
>>                          pci_map_addr = pci_find_max_end_va();
>>
>>                  bar_addr = pci_map_addr;
>> -               pci_map_addr = RTE_PTR_ADD(bar_addr, (size_t) reg.size);
>> +               pci_map_addr = RTE_PTR_ADD(bar_addr, (size_t) reg->size);
>>
>>                  maps[i].addr = bar_addr;
>> -               maps[i].offset = reg.offset;
>> -               maps[i].size = reg.size;
>> +               maps[i].offset = reg->offset;
>> +               maps[i].size = reg->size;
>>                  maps[i].path = NULL; /* vfio doesn't have per-resource paths */
>>
>>                  ret = pci_vfio_mmap_bar(vfio_dev_fd, vfio_res, i, 0);
>>                  if (ret < 0) {
>>                          RTE_LOG(ERR, EAL, "  %s mapping BAR%i failed: %s\n",
>>                                          pci_addr, i, strerror(errno));
>> +                       free(reg);
>>                          goto err_vfio_res;
>>                  }
>>
>>                  dev->mem_resource[i].addr = maps[i].addr;
>> +
>> +               free(reg);
>>          }
>>
>>          if (pci_rte_vfio_setup_device(dev, vfio_dev_fd) < 0) {
>> diff --git a/lib/librte_eal/common/include/rte_vfio.h b/lib/librte_eal/common/include/rte_vfio.h
>> index 5ca13fcce..f6617e004 100644
>> --- a/lib/librte_eal/common/include/rte_vfio.h
>> +++ b/lib/librte_eal/common/include/rte_vfio.h
>> @@ -14,6 +14,8 @@
>>   extern "C" {
>>   #endif
>>
>> +#include <stdint.h>
>> +
>>   /*
>>    * determine if VFIO is present on the system
>>    */
>> @@ -44,6 +46,30 @@ extern "C" {
>>   #define RTE_VFIO_NOIOMMU 8
>>   #endif
>>
>> +/*
>> + * capabilities are only supported on kernel 4.6+. there were also some API
>> + * changes as well, so add a macro to get cap offset.
>> + */
>> +#ifdef VFIO_REGION_INFO_FLAG_CAPS
>> +#define RTE_VFIO_INFO_FLAG_CAPS VFIO_REGION_INFO_FLAG_CAPS
>> +#define VFIO_CAP_OFFSET(x) (x->cap_offset)
>> +#else
>> +#define RTE_VFIO_INFO_FLAG_CAPS (1 << 3)
>> +#define VFIO_CAP_OFFSET(x) (x->resv)
>> +struct vfio_info_cap_header {
>> +       uint16_t id;
>> +       uint16_t version;
>> +       uint32_t next;
>> +};
>> +#endif
>> +
>> +/* kernels 4.16+ can map BAR containing MSI-X table */
>> +#ifdef VFIO_REGION_INFO_CAP_MSIX_MAPPABLE
>> +#define RTE_VFIO_CAP_MSIX_MAPPABLE VFIO_REGION_INFO_CAP_MSIX_MAPPABLE
>> +#else
>> +#define RTE_VFIO_CAP_MSIX_MAPPABLE 3
>> +#endif
>> +
>>   #else /* not VFIO_PRESENT */
>>
>>   /* we don't need an actual definition, only pointer is used */
>> --
>> 2.17.1
> 
> Hi Anatoly,
> Please fix the error check for ioctl in pci_vfio_region_info() from
> "if (ret)" to "if (ret < 0)"
> My environment reported compiler errors with -Werror=maybe-uninitialized).
> 
> dpdk/drivers/bus/pci/linux/pci_vfio.c: In function
> ‘pci_vfio_map_resource_primary’:
> dpdk/drivers/bus/pci/linux/pci_vfio.c:612:4: error: ‘reg’ may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
>      free(reg);
>      ^~~~~~~~~
> dpdk/drivers/bus/pci/linux/pci_vfio.c:495:2: error: ‘info’ may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
>    free(info);
>    ^~~~~~~~~~
> dpdk/drivers/bus/pci/linux/pci_vfio.c:485:27: note: ‘info’ was declared here
>    struct vfio_region_info *info;
> 
> 
> Other code looks good to me.
> I tested the updated patch with the above change and confirmed it
> could mmap BAR on my ppc64le machine.

Thanks!

I'll fix it for v3.

> 
> Thanks,
> Takeshi
> 


-- 
Thanks,
Anatoly