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Re: [Qemu-devel] [PATCH qemu v16 18/19] vfio/spapr: Create DMA window dy


From: Alex Williamson
Subject: Re: [Qemu-devel] [PATCH qemu v16 18/19] vfio/spapr: Create DMA window dynamically (SPAPR IOMMU v2)
Date: Mon, 16 May 2016 14:20:02 -0600

On Mon, 16 May 2016 14:52:41 +1000
Alexey Kardashevskiy <address@hidden> wrote:

> On 05/14/2016 08:26 AM, Alex Williamson wrote:
> > On Wed,  4 May 2016 16:52:30 +1000
> > Alexey Kardashevskiy <address@hidden> 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 <address@hidden>
> >> ---
> >> Changes:
> >> 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 | 133 
> >> ++++++++++++++++++++++++++++++++++++++++++++++++++-----
> >>  trace-events     |   2 +
> >>  2 files changed, 125 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >> index 03daf88..bd2dee8 100644
> >> --- a/hw/vfio/common.c
> >> +++ b/hw/vfio/common.c
> >> @@ -240,6 +240,18 @@ static int vfio_dma_map(VFIOContainer *container, 
> >> hwaddr iova,
> >>      return -errno;
> >>  }
> >>
> >> +static bool range_contains(hwaddr start, hwaddr end, hwaddr addr)
> >> +{
> >> +    return start <= addr && addr <= end;
> >> +}  
> >
> > a) If you want a "range_foo" function then put it in range.h
> > b) I suspect there are already range.h functions that can do this.
> >  
> >> +
> >> +static bool vfio_host_win_intersects(VFIOHostDMAWindow *hostwin,
> >> +                                     hwaddr min_iova, hwaddr max_iova)
> >> +{
> >> +    return range_contains(hostwin->min_iova, hostwin->min_iova, min_iova) 
> >> ||
> >> +        range_contains(min_iova, max_iova, hostwin->min_iova);
> >> +}  
> >
> > How is this different than ranges_overlap()?  
> >> +
> >>  static VFIOHostDMAWindow *vfio_host_win_lookup(VFIOContainer *container,
> >>                                                 hwaddr min_iova, hwaddr 
> >> max_iova)
> >>  {
> >> @@ -279,6 +291,14 @@ static int vfio_host_win_add(VFIOContainer *container,
> >>      return 0;
> >>  }
> >>
> >> +static void vfio_host_win_del(VFIOContainer *container, hwaddr min_iova)
> >> +{
> >> +    VFIOHostDMAWindow *hostwin = vfio_host_win_lookup(container, 
> >> min_iova, 1);
> >> +
> >> +    g_assert(hostwin);  
> >
> > Handle the error please.  
> 
> Will this be enough?
> 
>      if (!hostwin) {
>          error_report("%s: Cannot delete missing window at %"HWADDR_PRIx,
>                       __func__, min_iova);
>          return;
>      }

Better.  I was really thinking to return error to the caller, but if
the caller has no return path, perhaps this is as good as we can do.
Expect that I will push back on any assert() calls added to vfio.


> >> +    QLIST_REMOVE(hostwin, hostwin_next);
> >> +}
> >> +
> >>  static bool vfio_listener_skipped_section(MemoryRegionSection *section)
> >>  {
> >>      return (!memory_region_is_ram(section->mr) &&
> >> @@ -392,6 +412,69 @@ 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;
> >> +        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) };
> >> +
> >> +        trace_vfio_listener_region_add_iommu(iova, end);
> >> +        /*
> >> +         * 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);
> >> +        /*
> >> +         * 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;
> >> +
> >> +        /* For now intersections are not allowed, we may relax this later 
> >> */
> >> +        QLIST_FOREACH(hostwin, &container->hostwin_list, hostwin_next) {
> >> +            if (vfio_host_win_intersects(hostwin,
> >> +                    section->offset_within_address_space,
> >> +                    section->offset_within_address_space +
> >> +                    create.window_size - 1)) {
> >> +                goto fail;
> >> +            }
> >> +        }
> >> +
> >> +        ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_TCE_CREATE, &create);
> >> +        if (ret) {
> >> +            error_report("Failed to create a window, ret = %d (%m)", ret);
> >> +            goto fail;
> >> +        }
> >> +
> >> +        if (create.start_addr != section->offset_within_address_space) {
> >> +            struct vfio_iommu_spapr_tce_remove remove = {
> >> +                .argsz = sizeof(remove),
> >> +                .start_addr = 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);
> >> +            ret = -EINVAL;
> >> +            goto fail;
> >> +        }
> >> +        trace_vfio_spapr_create_window(create.page_shift,
> >> +                                       create.window_size,
> >> +                                       create.start_addr);
> >> +
> >> +        vfio_host_win_add(container, create.start_addr,
> >> +                          create.start_addr + create.window_size - 1,
> >> +                          1ULL << create.page_shift);
> >> +    }  
> >
> > This is a function on its own, split it out and why not stop pretending
> > prereg is some sort of generic interface and let's just make a spapr
> > support file.  
> 
> 
> Yet another new file - spapr.c, or rename prereg.c to spapr.c and add this 
> stuff there?

prereg.c is already spapr specific, so I'd rename it and potentially
add this to it.

> Also, what bits? I'd keep VFIOHostDMAWindow business in here and moved 
> vfio_iommu_spapr_tce_create and ioctl to the new place, will this be ok? 
> Thanks.

VFIOHostDMAWindow is actually generic, so keeping it here makes sense.
  
> >> +
> >>      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,
> >> @@ -566,6 +649,22 @@ static void vfio_listener_region_del(MemoryListener 
> >> *listener,
> >>                       container, iova, int128_get64(llsize), ret);
> >>      }
> >>
> >> +    if (container->iommu_type == VFIO_SPAPR_TCE_v2_IOMMU) {
> >> +        struct vfio_iommu_spapr_tce_remove remove = {
> >> +            .argsz = sizeof(remove),
> >> +            .start_addr = section->offset_within_address_space,
> >> +        };
> >> +        ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_TCE_REMOVE, &remove);
> >> +        if (ret) {
> >> +            error_report("Failed to remove window at %"PRIx64,
> >> +                         remove.start_addr);
> >> +        }
> >> +
> >> +        vfio_host_win_del(container, 
> >> section->offset_within_address_space);
> >> +
> >> +        trace_vfio_spapr_remove_window(remove.start_addr);
> >> +    }  
> >
> > This would be in that spapr file too.
> >  
> >> +
> >>      if (iommu && iommu->iommu_ops && iommu->iommu_ops->vfio_stop) {
> >>          iommu->iommu_ops->vfio_stop(section->mr);
> >>      }
> >> @@ -957,11 +1056,6 @@ 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) {
> >> @@ -970,11 +1064,30 @@ 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.
> >> +             */
> >> +            struct vfio_iommu_spapr_tce_remove remove = {
> >> +                .argsz = sizeof(remove),
> >> +                .start_addr = info.dma32_window_start,
> >> +            };
> >> +            ret = ioctl(fd, VFIO_IOMMU_SPAPR_TCE_REMOVE, &remove);
> >> +            if (ret) {
> >> +                error_report("vfio: VFIO_IOMMU_SPAPR_TCE_REMOVE failed: 
> >> %m");
> >> +                ret = -errno;
> >> +                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/trace-events b/trace-events
> >> index d0d8615..b5419de 100644
> >> --- a/trace-events
> >> +++ b/trace-events
> >> @@ -1739,6 +1739,8 @@ vfio_region_finalize(const char *name, int index) 
> >> "Device %s, region %d"
> >>  vfio_region_mmaps_set_enabled(const char *name, bool enabled) "Region %s 
> >> mmaps enabled: %d"
> >>  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"  
> >  
> 
> 




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