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

[Alexey Kardashevskiy <aik@ozlabs.ru>]

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On 03/06/16 17:37, David Gibson wrote:
> 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.

I suppose so, I'll change this.


>> +
>> +    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.


And do what here? vfio_spapr_remove_window() calls error_report() already
and I still want to remove the host window 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.

Well, this way it felt more obvious that pagesize is a single page size,
not a mask. Not sure if memory_region_iommu_get_page_sizes() returning a
mask (rather than a page size) is a good idea after all...

I'll make it:

 create.page_shift = ctz64(pagesizes);

and (below):

 *pgsize = 1ULL << create.page_shift;


and remove pagesize.

>> +    /*
>> +     * 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"
> 


-- 
Alexey


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