Re: [Qemu-devel] [PATCH qemu v15 16/17] vfio/spapr: Use VFIO_SPAPR_TCE_v2_IOMMU

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

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On Wed, Apr 20, 2016 at 07:43:41PM +1000, Alexey Kardashevskiy wrote:
> On 04/07/2016 11:10 AM, David Gibson wrote:
> >Subject doesn't seem quite right, since you added at least minimal
> >support for the SPAPRv2 IOMMU in the prereg patch.
> >
> >On Mon, Apr 04, 2016 at 07:33:45PM +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 euristic to decide on the TCE table
> >>levels number.
> >
> >"heuristic" has an 'h' (yes, English spelling is stupid[0]).
> >
> >[0] The historical reasons for that are kind of fascinating, though.
> 
> Tried googling, could not spot quickly the reasoning, any hints what to
> google for? Or just a link with an explanation? :)

That wasn't a comment about heuristic specifically, but english
spelling in general.  I got most of the fascinating stuff I've seen
from:

http://www.amazon.com/Spell-Out-Enthralling-Extraordinary-Spelling/dp/1250056128/ref=la_B000AP940C_1_5/189-2461131-2789630?s=books&ie=UTF8&qid=1461211129&sr=1-5

> >>This should cause no guest visible change in behavior.
> >>
> >>Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> >>---
> >>Changes:
> >>v14:
> >>* new to the series
> >>
> >>---
> >>TODO:
> >>* export levels to PHB
> >>---
> >>  hw/vfio/common.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
> >>  trace-events     |   2 +
> >>  2 files changed, 107 insertions(+), 10 deletions(-)
> >>
> >>diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >>index 5e5b77c..57a51df 100644
> >>--- a/hw/vfio/common.c
> >>+++ b/hw/vfio/common.c
> >>@@ -279,6 +279,14 @@ 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);
> >>+    QLIST_REMOVE(hostwin, hiommu_next);
> >>+}
> >>+
> >>  static bool vfio_listener_skipped_section(MemoryRegionSection *section)
> >>  {
> >>      return (!memory_region_is_ram(section->mr) &&
> >>@@ -392,6 +400,63 @@ static void vfio_listener_region_add(MemoryListener *listener,
> >>      }
> >>      end = int128_get64(llend);
> >>
> >>+    if (container->iommu_type == VFIO_SPAPR_TCE_v2_IOMMU) {
> >
> >I think the "add region" path could do with being split out into a
> >different function - vfio_listener_region_add() is getting pretty
> >huge.
> 
> It is big but not huge and I am trying to avoid having functions with
> "spapr" in their names in common.c as once they appear, we will start having
> a discussion if they should move to a separate file and if they do, then may
> be some other code should too, etc...

I don't think it needs to be a "spapr" named function.  The spapr
backend is the only one to support it for now, but other iommus could
support dynamic windows in future (for example, if I ever get time to
implement the "type2" converged interface I was thinking about, I'd
look to include that).

> >>+        unsigned entries, pages, pagesize = qemu_real_host_page_size;
> >>+        struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
> >>+
> >>+        trace_vfio_listener_region_add_iommu(iova, end - 1);
> >>+        if (section->mr->iommu_ops) {
> >>+            pagesize = section->mr->iommu_ops->get_page_sizes(section->mr);
> >
> >Since you're querying the guest IOMMU here, I assume pagesize is
> >supposed to represent *guest* IOMMU pagesizes, in which case it should
> >default to TARGET_PAGE_SIZE, instead of qemu_real_host_page_size.
> >(didn't you already have a function which implemented that fallback?)
> 
> Yes, will use the helper.
> 
> 
> >>+        }
> >>+        /*
> >>+         * 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
> >>+         * euristic to decide how many levels we want for our table:
> >
> >s/some euristic/a heuristic/
> >
> >>+         * 0..64 = 1; 65..4096 = 2; 4097..262144 = 3; 262145.. = 4
> >>+         */
> >>+        entries = create.window_size >> create.page_shift;
> >>+        pages = (entries * sizeof(uint64_t)) / getpagesize();
> >>+        create.levels = ctz64(pow2ceil(pages) - 1) / 6 + 1;
> >>+
> >>+        if (vfio_host_win_lookup(container, create.start_addr,
> >>+                                 create.start_addr + create.window_size - 1)) {
> >>+            goto fail;
> >
> >Hmm.. if you successfully look up a host window, it seems to me you
> >shouldn't fail, but in fact don't even need to create a new window
> >(the removal path gets harder though, because you need to check if any
> >guest window requires that host window).
> 
> 
> At the moment if the window is there, it is failure in the environment I am
> testing it in. And, having a host kernel which cannot allocate and map
> windows randomly, it is unlikely that I'll have a setup where this spot
> won't mean that something went wrong. x86 case needs lot more than this
> anyway.

Hm, I suppose so.

> 
> 
> >Requiring that the host windows exactly match the guest windows is
> >probably ok for a first version - except that in that case any overlap
> >should cause a failure, not just a complete inclusion.
> 
> Yes, for now this should fail too, I'll fix it.
> 
> 
> >
> >>+        }
> >>+
> >>+        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);
> >>+    }
> >>+
> >>      if (!vfio_host_win_lookup(container, iova, end - 1)) {
> >>          error_report("vfio: IOMMU container %p can't map guest IOVA region"
> >>                       " 0x%"HWADDR_PRIx"..0x%"HWADDR_PRIx,
> >>@@ -525,6 +590,22 @@ static void vfio_listener_region_del(MemoryListener *listener,
> >>                       container, iova, end - iova, 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);
> >>+    }
> >>+
> >>      if (iommu && iommu->iommu_ops && iommu->iommu_ops->vfio_stop) {
> >>          iommu->iommu_ops->vfio_stop(section->mr);
> >>      }
> >>@@ -915,11 +996,6 @@ 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) {
> >>@@ -928,11 +1004,30 @@ 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 23ca0b9..5c651fa 100644
> >>--- a/trace-events
> >>+++ b/trace-events
> >>@@ -1738,6 +1738,8 @@ 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"
> >
> 
> 

-- 
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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