Re: [Qemu-devel] [Qemu-ppc] [PATCH qemu v13 11/16] vfio: spapr: Add SPAPR IOMMU v2 support (DMA memory preregistering)

[David Gibson]

On Tue, Mar 15, 2016 at 01:53:48PM +1100, Alexey Kardashevskiy wrote:
> On 03/03/2016 05:30 PM, David Gibson wrote:
> >On Tue, Mar 01, 2016 at 08:10:36PM +1100, Alexey Kardashevskiy wrote:
> >>This makes use of the new "memory registering" feature. The idea is
> >>to provide the userspace ability to notify the host kernel about pages
> >>which are going to be used for DMA. Having this information, the host
> >>kernel can pin them all once per user process, do locked pages
> >>accounting (once) and not spent time on doing that in real time with
> >>possible failures which cannot be handled nicely in some cases.
> >>
> >>This adds a prereg memory listener which listens on address_space_memory
> >>and notifies a VFIO container about memory which needs to be
> >>pinned/unpinned. VFIO MMIO regions (i.e. "skip dump" regions) are skipped.
> >>
> >>As there is no per-IOMMU-type release() callback anymore, this stores
> >>the IOMMU type in the container so vfio_listener_release() can device
> >>if it needs to unregister @prereg_listener.
> >>
> >>The feature is only enabled for SPAPR IOMMU v2. The host kernel changes
> >>are required. Since v2 does not need/support VFIO_IOMMU_ENABLE, this does
> >>not call it when v2 is detected and enabled.
> >>
> >>This does not change the guest visible interface.
> >>
> >>Signed-off-by: Alexey Kardashevskiy <address@hidden>
> >>---
> >>  hw/vfio/Makefile.objs         |   1 +
> >>  hw/vfio/common.c              |  39 +++++++++---
> >>  hw/vfio/prereg.c              | 138 
> >> ++++++++++++++++++++++++++++++++++++++++++
> >>  include/hw/vfio/vfio-common.h |   4 ++
> >>  trace-events                  |   2 +
> >>  5 files changed, 175 insertions(+), 9 deletions(-)
> >>  create mode 100644 hw/vfio/prereg.c
> >>
> >>diff --git a/hw/vfio/Makefile.objs b/hw/vfio/Makefile.objs
> >>index ceddbb8..5800e0e 100644
> >>--- a/hw/vfio/Makefile.objs
> >>+++ b/hw/vfio/Makefile.objs
> >>@@ -4,4 +4,5 @@ obj-$(CONFIG_PCI) += pci.o pci-quirks.o
> >>  obj-$(CONFIG_SOFTMMU) += platform.o
> >>  obj-$(CONFIG_SOFTMMU) += calxeda-xgmac.o
> >>  obj-$(CONFIG_SOFTMMU) += amd-xgbe.o
> >>+obj-$(CONFIG_SOFTMMU) += prereg.o
> >>  endif
> >>diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >>index 3aaa6b5..f2a03e0 100644
> >>--- a/hw/vfio/common.c
> >>+++ b/hw/vfio/common.c
> >>@@ -531,6 +531,9 @@ static const MemoryListener vfio_iommu_listener = {
> >>  static void vfio_listener_release(VFIOContainer *container)
> >>  {
> >>      memory_listener_unregister(&container->iommu_listener.listener);
> >>+    if (container->iommu_type == VFIO_SPAPR_TCE_v2_IOMMU) {
> >>+        memory_listener_unregister(&container->prereg_listener.listener);
> >>+    }
> >>  }
> >>
> >>  int vfio_mmap_region(Object *obj, VFIORegion *region,
> >>@@ -722,8 +725,8 @@ static int vfio_connect_container(VFIOGroup *group, 
> >>AddressSpace *as)
> >>              goto free_container_exit;
> >>          }
> >>
> >>-        ret = ioctl(fd, VFIO_SET_IOMMU,
> >>-                    v2 ? VFIO_TYPE1v2_IOMMU : VFIO_TYPE1_IOMMU);
> >>+        container->iommu_type = v2 ? VFIO_TYPE1v2_IOMMU : VFIO_TYPE1_IOMMU;
> >>+        ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
> >>          if (ret) {
> >>              error_report("vfio: failed to set iommu for container: %m");
> >>              ret = -errno;
> >>@@ -748,8 +751,10 @@ static int vfio_connect_container(VFIOGroup *group, 
> >>AddressSpace *as)
> >>          if ((ret == 0) && (info.flags & VFIO_IOMMU_INFO_PGSIZES)) {
> >>              container->iova_pgsizes = info.iova_pgsizes;
> >>          }
> >>-    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU)) {
> >>+    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU) ||
> >>+               ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_v2_IOMMU)) {
> >>          struct vfio_iommu_spapr_tce_info info;
> >>+        bool v2 = !!ioctl(fd, VFIO_CHECK_EXTENSION, 
> >>VFIO_SPAPR_TCE_v2_IOMMU);
> >>
> >>          ret = ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &fd);
> >>          if (ret) {
> >>@@ -757,7 +762,9 @@ static int vfio_connect_container(VFIOGroup *group, 
> >>AddressSpace *as)
> >>              ret = -errno;
> >>              goto free_container_exit;
> >>          }
> >>-        ret = ioctl(fd, VFIO_SET_IOMMU, VFIO_SPAPR_TCE_IOMMU);
> >>+        container->iommu_type =
> >>+            v2 ? VFIO_SPAPR_TCE_v2_IOMMU : VFIO_SPAPR_TCE_IOMMU;
> >>+        ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
> >
> >It'd be nice to consolidate the setting of container->iommu_type and
> >then the SET_IOMMU ioctl() rather than having more or less duplicated
> >logic for Type1 and SPAPR, but it's not a big deal.
> 
> 
> May be but I cannot think of any nice way of doing this though.
> 
> 
> >
> >>          if (ret) {
> >>              error_report("vfio: failed to set iommu for container: %m");
> >>              ret = -errno;
> >>@@ -769,11 +776,25 @@ static int vfio_connect_container(VFIOGroup *group, 
> >>AddressSpace *as)
> >>           * when container fd is closed so we do not call it explicitly
> >>           * in this file.
> >>           */
> >>-        ret = ioctl(fd, VFIO_IOMMU_ENABLE);
> >>-        if (ret) {
> >>-            error_report("vfio: failed to enable container: %m");
> >>-            ret = -errno;
> >>-            goto free_container_exit;
> >>+        if (!v2) {
> >>+            ret = ioctl(fd, VFIO_IOMMU_ENABLE);
> >>+            if (ret) {
> >>+                error_report("vfio: failed to enable container: %m");
> >>+                ret = -errno;
> >>+                goto free_container_exit;
> >>+            }
> >>+        } else {
> >>+            container->prereg_listener.container = container;
> >>+            container->prereg_listener.listener = vfio_prereg_listener;
> >>+
> >>+            memory_listener_register(&container->prereg_listener.listener,
> >>+                                     &address_space_memory);
> >
> >This assumes that the target address space of the (guest) IOMMU is
> >address_space_memory.  Which is fine - vfio already assumes that - but
> >it reminds me that it'd be nice to have an explicit check for that (I
> >guess it would have to go in vfio_iommu_map_notify()).  So that if
> >someone constructs a machine where that's not the case, it'll at least
> >be obvious why VFIO isn't working.
> 
> Ok, I'll add a small patch for this in the next respin.

Ok.

> >>+            if (container->error) {
> >>+                error_report("vfio: RAM memory listener initialization 
> >>failed for container");
> >>+                memory_listener_unregister(
> >>+                    &container->prereg_listener.listener);
> >>+                goto free_container_exit;
> >>+            }
> >>          }
> >
> >Looks like you don't have an error path which will handle the case
> >where the prereg listener is registered, but registering the normal
> >PCI AS listener fails - I believe you will fail to unregister the
> >prereg listener in that case.
> 
> 
> In this case, the control goes to listener_release_exit: which calls
> vfio_listener_release() which unregisters both listeners (it is a few chunks
> above).

Ah.. yes.  In which case this could also jump to listener_release_exit
and avoid the explicit unreg(), yes?

> >>          /*
> >>diff --git a/hw/vfio/prereg.c b/hw/vfio/prereg.c
> >>new file mode 100644
> >>index 0000000..66cd696
> >>--- /dev/null
> >>+++ b/hw/vfio/prereg.c
> >>@@ -0,0 +1,138 @@
> >>+/*
> >>+ * DMA memory preregistration
> >>+ *
> >>+ * Authors:
> >>+ *  Alexey Kardashevskiy <address@hidden>
> >>+ *
> >>+ * This work is licensed under the terms of the GNU GPL, version 2.  See
> >>+ * the COPYING file in the top-level directory.
> >>+ */
> >>+
> >>+#include "qemu/osdep.h"
> >>+#include <sys/ioctl.h>
> >>+#include <linux/vfio.h>
> >>+
> >>+#include "hw/vfio/vfio-common.h"
> >>+#include "hw/vfio/vfio.h"
> >>+#include "qemu/error-report.h"
> >>+#include "trace.h"
> >>+
> >>+static bool vfio_prereg_listener_skipped_section(MemoryRegionSection 
> >>*section)
> >>+{
> >>+    return (!memory_region_is_ram(section->mr) &&
> >>+            !memory_region_is_iommu(section->mr)) ||
> >>+            memory_region_is_skip_dump(section->mr);
> >>+}
> >>+
> >>+static void vfio_prereg_listener_region_add(MemoryListener *listener,
> >>+                                            MemoryRegionSection *section)
> >>+{
> >>+    VFIOMemoryListener *vlistener = container_of(listener, 
> >>VFIOMemoryListener,
> >>+                                                 listener);
> >>+    VFIOContainer *container = vlistener->container;
> >>+    hwaddr iova;
> >>+    Int128 llend;
> >>+    int ret;
> >>+    hwaddr page_mask = qemu_real_host_page_mask;
> >>+    struct vfio_iommu_spapr_register_memory reg = {
> >>+        .argsz = sizeof(reg),
> >>+        .flags = 0,
> >>+    };
> >>+
> >>+    if (vfio_prereg_listener_skipped_section(section)) {
> >>+        trace_vfio_listener_region_add_skip(
> >>+                section->offset_within_address_space,
> >>+                section->offset_within_address_space +
> >>+                int128_get64(int128_sub(section->size, int128_one())));
> >>+        return;
> >>+    }
> >
> >You should probably explicitly check for IOMMU regions and abort if
> >you find one.  An IOMMU AS appearing within address_space_memory would
> >be bad news.
> 
> 
> Oh, vfio_prereg_listener_skipped_section() allows memory_region_is_iommu(),
> I'll remove it.

Well, that's part.

But IOMMU regions appearing here shouldn't just be ignored - they
should be treated as a fatal error.

> 
> 
> 
> >
> >>+    if (unlikely((section->offset_within_address_space & ~page_mask) !=
> >>+                 (section->offset_within_region & ~page_mask))) {
> >>+        error_report("%s received unaligned region", __func__);
> >>+        return;
> >>+    }
> >>+
> >>+    iova = ROUND_UP(section->offset_within_address_space, ~page_mask + 1);
> >
> >iova is a terrible name here.  This is *not* an IOVA, but a real
> >memory address.
> 
> 
> I'll do s/iova/gpa/

Good.

> 
> 
> >
> >>+    llend = int128_make64(section->offset_within_address_space);
> >>+    llend = int128_add(llend, section->size);
> >>+    llend = int128_and(llend, int128_exts64(page_mask));
> >>+
> >>+    if (int128_ge(int128_make64(iova), llend)) {
> >>+        return;
> >
> >IIUC, if we get here something has gone horribly wrong in our machine
> >setup, and we shold probably just abort.  Same goes for the similar
> >test in the IOVA listener, of course.
> 
> 
> I do not have a good message candidate though. May be
> hw_error("vfio: Broken section alignment");
> ?

Just an assert should be fine.

> 
> 
> >
> >>+    }
> >>+
> >>+    memory_region_ref(section->mr);
> >>+
> >>+    reg.vaddr = (__u64) memory_region_get_ram_ptr(section->mr) +
> >>+        section->offset_within_region +
> >>+        (iova - section->offset_within_address_space);
> >>+    reg.size = int128_get64(llend) - iova;
> >>+
> >>+    ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_REGISTER_MEMORY, &reg);
> >>+    trace_vfio_ram_register(reg.vaddr, reg.size, ret ? -errno : 0);
> >>+    if (ret) {
> >>+        /*
> >>+         * On the initfn path, store the first error in the container so we
> >>+         * can gracefully fail.  Runtime, there's not much we can do other
> >>+         * than throw a hardware error.
> >>+         */
> >>+        if (!container->initialized) {
> >>+            if (!container->error) {
> >>+                container->error = ret;
> >>+            }
> >>+        } else {
> >>+            hw_error("vfio: DMA mapping failed, unable to continue");
> >
> >Wrong error message.
> >
> >>+        }
> >>+    }
> >>+}
> >>+
> >>+static void vfio_prereg_listener_region_del(MemoryListener *listener,
> >>+                                            MemoryRegionSection *section)
> >>+{
> >>+    VFIOMemoryListener *vlistener = container_of(listener, 
> >>VFIOMemoryListener,
> >>+                                                 listener);
> >>+    VFIOContainer *container = vlistener->container;
> >>+    hwaddr iova, end;
> >>+    int ret;
> >>+    hwaddr page_mask = qemu_real_host_page_mask;
> >>+    struct vfio_iommu_spapr_register_memory reg = {
> >>+        .argsz = sizeof(reg),
> >>+        .flags = 0,
> >>+    };
> >>+
> >>+    if (vfio_prereg_listener_skipped_section(section)) {
> >>+        trace_vfio_listener_region_del_skip(
> >>+                section->offset_within_address_space,
> >>+                section->offset_within_address_space +
> >>+                int128_get64(int128_sub(section->size, int128_one())));
> >>+        return;
> >>+    }
> >>+
> >>+    if (unlikely((section->offset_within_address_space & ~page_mask) !=
> >>+                 (section->offset_within_region & ~page_mask))) {
> >>+        error_report("%s received unaligned region", __func__);
> >>+        return;
> >>+    }
> >>+
> >>+    iova = ROUND_UP(section->offset_within_address_space, ~page_mask + 1);
> >>+    end = (section->offset_within_address_space + 
> >>int128_get64(section->size)) &
> >>+        page_mask;
> >>+
> >>+    if (iova >= end) {
> >>+        return;
> >>+    }
> >>+
> >>+    reg.vaddr = (__u64) memory_region_get_ram_ptr(section->mr) +
> >>+        section->offset_within_region +
> >>+        (iova - section->offset_within_address_space);
> >>+    reg.size = end - iova;
> >>+
> >>+    ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY, &reg);
> >>+    trace_vfio_ram_unregister(reg.vaddr, reg.size, ret ? -errno : 0);
> >>+}
> >>+
> >>+const MemoryListener vfio_prereg_listener = {
> >>+    .region_add = vfio_prereg_listener_region_add,
> >>+    .region_del = vfio_prereg_listener_region_del,
> >>+};
> >>diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> >>index b6b736c..bcbc5cb 100644
> >>--- a/include/hw/vfio/vfio-common.h
> >>+++ b/include/hw/vfio/vfio-common.h
> >>@@ -70,6 +70,8 @@ typedef struct VFIOContainer {
> >>      VFIOAddressSpace *space;
> >>      int fd; /* /dev/vfio/vfio, empowered by the attached groups */
> >>      VFIOMemoryListener iommu_listener;
> >>+    VFIOMemoryListener prereg_listener;
> >>+    unsigned iommu_type;
> >>      int error;
> >>      bool initialized;
> >>      /*
> >>@@ -146,4 +148,6 @@ extern const MemoryRegionOps vfio_region_ops;
> >>  extern QLIST_HEAD(vfio_group_head, VFIOGroup) vfio_group_list;
> >>  extern QLIST_HEAD(vfio_as_head, VFIOAddressSpace) vfio_address_spaces;
> >>
> >>+extern const MemoryListener vfio_prereg_listener;
> >>+
> >>  #endif /* !HW_VFIO_VFIO_COMMON_H */
> >>diff --git a/trace-events b/trace-events
> >>index 4b6ea70..f5335ec 100644
> >>--- a/trace-events
> >>+++ b/trace-events
> >>@@ -1725,6 +1725,8 @@ vfio_disconnect_container(int fd) "close 
> >>container->fd=%d"
> >>  vfio_put_group(int fd) "close group->fd=%d"
> >>  vfio_get_device(const char * name, unsigned int flags, unsigned int 
> >> num_regions, unsigned int num_irqs) "Device %s flags: %u, regions: %u, 
> >> irqs: %u"
> >>  vfio_put_base_device(int fd) "close vdev->fd=%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"
> >>
> >>  # hw/vfio/platform.c
> >>  vfio_platform_populate_regions(int region_index, unsigned long flag, 
> >> unsigned long size, int fd, unsigned long offset) "- region %d flags = 
> >> 0x%lx, size = 0x%lx, fd= %d, offset = 0x%lx"
> >
> 
> 

-- 
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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