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 Mon, Jun 06, 2016 at 04:45:50PM +1000, Alexey Kardashevskiy wrote:
> 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.

Hmm.. yes, I guess so.  Probably best to have a comment here saying
why it's safe to ignore an error you should usually test for.

> > 
> >> +        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;

Yes, I think that's better.

> 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"
> > 
> 
> 




-- 
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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