Re: [Qemu-devel] [PATCH qemu v17 10/12] vfio/spapr: Create DMA window dynamically (SPAPR IOMMU v2)

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Jun 01, 2016 at 06:57:41PM +1000, Alexey Kardashevskiy wrote:
> New VFIO_SPAPR_TCE_v2_IOMMU type supports dynamic DMA window management.
> This adds ability to VFIO common code to dynamically allocate/remove
> DMA windows in the host kernel when new VFIO container is added/removed.
> 
> This adds VFIO_IOMMU_SPAPR_TCE_CREATE ioctl to vfio_listener_region_add
> and adds just created IOMMU into the host IOMMU list; the opposite
> action is taken in vfio_listener_region_del.
> 
> When creating a new window, this uses heuristic to decide on the TCE table
> levels number.
> 
> This should cause no guest visible change in behavior.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> Changes:
> v17:
> * moved spapr window create/remove helpers to separate file
> * added hw_error() if vfio_host_win_del() failed
> 
> v16:
> * used memory_region_iommu_get_page_sizes() in vfio_listener_region_add()
> * enforced no intersections between windows
> 
> v14:
> * new to the series
> ---
>  hw/vfio/common.c              | 76 +++++++++++++++++++++++++++++++++++++------
>  hw/vfio/spapr.c               | 70 +++++++++++++++++++++++++++++++++++++++
>  include/hw/vfio/vfio-common.h |  6 ++++
>  trace-events                  |  2 ++
>  4 files changed, 144 insertions(+), 10 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 52b08fd..7f55c26 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -275,6 +275,18 @@ static void vfio_host_win_add(VFIOContainer *container,
>      QLIST_INSERT_HEAD(&container->hostwin_list, hostwin, hostwin_next);
>  }
>  
> +static int vfio_host_win_del(VFIOContainer *container, hwaddr min_iova)
> +{
> +    VFIOHostDMAWindow *hostwin = vfio_host_win_lookup(container, min_iova, 1);

Hrm.. and for this case I think you want exact match, rather than
looking for range inclusion.

> +
> +    if (!hostwin) {
> +        return -1;
> +    }
> +    QLIST_REMOVE(hostwin, hostwin_next);
> +
> +    return 0;
> +}
> +
>  static bool vfio_listener_skipped_section(MemoryRegionSection *section)
>  {
>      return (!memory_region_is_ram(section->mr) &&
> @@ -388,6 +400,30 @@ static void vfio_listener_region_add(MemoryListener *listener,
>      }
>      end = int128_get64(int128_sub(llend, int128_one()));
>  
> +    if (container->iommu_type == VFIO_SPAPR_TCE_v2_IOMMU) {
> +        VFIOHostDMAWindow *hostwin;
> +        hwaddr pgsize = 0;
> +
> +        /* For now intersections are not allowed, we may relax this later */
> +        QLIST_FOREACH(hostwin, &container->hostwin_list, hostwin_next) {
> +            if (ranges_overlap(hostwin->min_iova,
> +                               hostwin->max_iova - hostwin->min_iova + 1,
> +                               section->offset_within_address_space,
> +                               int128_get64(section->size))) {
> +                goto fail;
> +            }
> +        }
> +
> +        ret = vfio_spapr_create_window(container, section, &pgsize);
> +        if (ret) {
> +            goto fail;
> +        }
> +
> +        vfio_host_win_add(container, section->offset_within_address_space,
> +                          section->offset_within_address_space +
> +                          int128_get64(section->size) - 1, pgsize);
> +    }
> +
>      if (!vfio_host_win_lookup(container, iova, end)) {
>          error_report("vfio: IOMMU container %p can't map guest IOVA region"
>                       " 0x%"HWADDR_PRIx"..0x%"HWADDR_PRIx,
> @@ -523,6 +559,18 @@ static void vfio_listener_region_del(MemoryListener *listener,
>                       "0x%"HWADDR_PRIx") = %d (%m)",
>                       container, iova, int128_get64(llsize), ret);
>      }
> +
> +    if (container->iommu_type == VFIO_SPAPR_TCE_v2_IOMMU) {
> +        vfio_spapr_remove_window(container,
> +                                 section->offset_within_address_space);

Should check for error here.

> +        if (vfio_host_win_del(container,
> +                              section->offset_within_address_space) < 0) {
> +            hw_error("%s: Cannot delete missing window at %"HWADDR_PRIx,
> +                     __func__, section->offset_within_address_space);

Personally I think assert() would be better here, but Alex doesn't
like them so I'm ok with this.

> +        }
> +
> +        trace_vfio_spapr_remove_window(section->offset_within_address_space);
> +    }
>  }
>  
>  static const MemoryListener vfio_memory_listener = {
> @@ -960,11 +1008,6 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>              }
>          }
>  
> -        /*
> -         * This only considers the host IOMMU's 32-bit window.  At
> -         * some point we need to add support for the optional 64-bit
> -         * window and dynamic windows
> -         */
>          info.argsz = sizeof(info);
>          ret = ioctl(fd, VFIO_IOMMU_SPAPR_TCE_GET_INFO, &info);
>          if (ret) {
> @@ -973,11 +1016,24 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>              goto listener_release_exit;
>          }
>  
> -        /* The default table uses 4K pages */
> -        vfio_host_win_add(container, info.dma32_window_start,
> -                          info.dma32_window_start +
> -                          info.dma32_window_size - 1,
> -                          0x1000);
> +        if (v2) {
> +            /*
> +             * There is a default window in just created container.
> +             * To make region_add/del simpler, we better remove this
> +             * window now and let those iommu_listener callbacks
> +             * create/remove them when needed.
> +             */
> +            ret = vfio_spapr_remove_window(container, info.dma32_window_start);
> +            if (ret) {
> +                goto free_container_exit;
> +            }
> +        } else {
> +            /* The default table uses 4K pages */
> +            vfio_host_win_add(container, info.dma32_window_start,
> +                              info.dma32_window_start +
> +                              info.dma32_window_size - 1,
> +                              0x1000);
> +        }
>      } else {
>          error_report("vfio: No available IOMMU models");
>          ret = -EINVAL;
> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> index f339472..0c784c4 100644
> --- a/hw/vfio/spapr.c
> +++ b/hw/vfio/spapr.c
> @@ -135,3 +135,73 @@ const MemoryListener vfio_prereg_listener = {
>      .region_add = vfio_prereg_listener_region_add,
>      .region_del = vfio_prereg_listener_region_del,
>  };
> +
> +int vfio_spapr_create_window(VFIOContainer *container,
> +                             MemoryRegionSection *section,
> +                             hwaddr *pgsize)
> +{
> +    int ret;
> +    unsigned pagesizes = memory_region_iommu_get_page_sizes(section->mr);
> +    unsigned pagesize = (hwaddr)1 << ctz64(pagesizes);
> +    unsigned entries, pages;
> +    struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
> +
> +    /*
> +     * FIXME: For VFIO iommu types which have KVM acceleration to
> +     * avoid bouncing all map/unmaps through qemu this way, this
> +     * would be the right place to wire that up (tell the KVM
> +     * device emulation the VFIO iommu handles to use).
> +     */
> +    create.window_size = int128_get64(section->size);
> +    create.page_shift = ctz64(pagesize);

Doing a ctz on a value which is defined as 1 << n seems a bit
perverse.

> +    /*
> +     * SPAPR host supports multilevel TCE tables, there is some
> +     * heuristic to decide how many levels we want for our table:
> +     * 0..64 = 1; 65..4096 = 2; 4097..262144 = 3; 262145.. = 4
> +     */
> +    entries = create.window_size >> create.page_shift;
> +    pages = MAX((entries * sizeof(uint64_t)) / getpagesize(), 1);
> +    pages = MAX(pow2ceil(pages) - 1, 1); /* Round up */
> +    create.levels = ctz64(pages) / 6 + 1;
> +
> +    ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_TCE_CREATE, &create);
> +    if (ret) {
> +        error_report("Failed to create a window, ret = %d (%m)", ret);
> +        return -errno;
> +    }
> +
> +    if (create.start_addr != section->offset_within_address_space) {
> +        vfio_spapr_remove_window(container, create.start_addr);
> +
> +        error_report("Host doesn't support DMA window at %"HWADDR_PRIx", must be %"PRIx64,
> +                     section->offset_within_address_space,
> +                     create.start_addr);
> +        ioctl(container->fd, VFIO_IOMMU_SPAPR_TCE_REMOVE, &remove);
> +        return -EINVAL;
> +    }
> +    trace_vfio_spapr_create_window(create.page_shift,
> +                                   create.window_size,
> +                                   create.start_addr);
> +    *pgsize = pagesize;
> +
> +    return 0;
> +}
> +
> +int vfio_spapr_remove_window(VFIOContainer *container,
> +                             hwaddr offset_within_address_space)
> +{
> +    struct vfio_iommu_spapr_tce_remove remove = {
> +        .argsz = sizeof(remove),
> +        .start_addr = offset_within_address_space,
> +    };
> +    int ret;
> +
> +    ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_TCE_REMOVE, &remove);
> +    if (ret) {
> +        error_report("Failed to remove window at %"PRIx64,
> +                     remove.start_addr);
> +        return -errno;
> +    }
> +
> +    return 0;
> +}
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index c76ddc4..7e80382 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -167,4 +167,10 @@ int vfio_get_dev_region_info(VFIODevice *vbasedev, uint32_t type,
>  #endif
>  extern const MemoryListener vfio_prereg_listener;
>  
> +int vfio_spapr_create_window(VFIOContainer *container,
> +                             MemoryRegionSection *section,
> +                             hwaddr *pgsize);
> +int vfio_spapr_remove_window(VFIOContainer *container,
> +                             hwaddr offset_within_address_space);
> +
>  #endif /* !HW_VFIO_VFIO_COMMON_H */
> diff --git a/trace-events b/trace-events
> index ddb8676..ec32c20 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -1768,6 +1768,8 @@ vfio_region_sparse_mmap_entry(int i, unsigned long start, unsigned long end) "sp
>  vfio_get_dev_region(const char *name, int index, uint32_t type, uint32_t subtype) "%s index %d, %08x/%0x8"
>  vfio_ram_register(uint64_t va, uint64_t size, int ret) "va=%"PRIx64" size=%"PRIx64" ret=%d"
>  vfio_ram_unregister(uint64_t va, uint64_t size, int ret) "va=%"PRIx64" size=%"PRIx64" ret=%d"
> +vfio_spapr_create_window(int ps, uint64_t ws, uint64_t off) "pageshift=0x%x winsize=0x%"PRIx64" offset=0x%"PRIx64
> +vfio_spapr_remove_window(uint64_t off) "offset=%"PRIx64
>  
>  # hw/vfio/platform.c
>  vfio_platform_base_device_init(char *name, int groupid) "%s belongs to group #%d"

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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