Re: [Qemu-ppc] [PATCH qemu v5 06/12] vfio: spapr: Add SPAPR IOMMU v2 support (DMA memory preregistering)

[David Gibson]

On Wed, Apr 08, 2015 at 02:05:28PM +1000, Alexey Kardashevskiy wrote:
> On 04/08/2015 12:15 PM, David Gibson wrote:
> >On Tue, Mar 31, 2015 at 04:28:41PM +1100, Alexey Kardashevskiy wrote:
> >>This makes use of the new "memory registering" feature. The idea is
> >>to provide the guest ability to notify the host kernel about pages which
> >
> >AFAICT it's not really the guest informing the host, just qemu
> >informing the host.  If I'm reading the code correctly, qemu registers
> >all RAM regionns, without guest intervention.
> 
> Right. Wrong commit log, I'll fix it.
> 
> 
> >>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 guest RAM memory listener which notifies a VFIO container
> >>about memory which needs to be pinned/unpinned. VFIO MMIO regions
> >>(i.e. "skip dump" regions) are skipped.
> >>
> >>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.
> >
> >So I'm clear, the v2 just represents a new userspace<->host kernel
> >interface for controlling the IOMMU, doesn't it?  It doesn't change
> >the guest visible IOMMU interface and doesn't represent different
> >IOMMU hardware?
> 
> 
> Exactly true.
> 
> 
> >>Signed-off-by: Alexey Kardashevskiy <address@hidden>
> >>---
> >>Changes:
> >>v5:
> >>* simplified the patch
> >>* added trace points
> >>* added round_up() for the size
> >>* SPAPR IOMMU v2 used
> >>---
> >>  hw/vfio/common.c              | 26 +++++++++-----
> >>  hw/vfio/spapr.c               | 79 
> >> +++++++++++++++++++++++++++++++++++++++++--
> >>  include/hw/vfio/vfio-common.h |  5 ++-
> >>  trace-events                  |  1 +
> >>  4 files changed, 100 insertions(+), 11 deletions(-)
> >>
> >>diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >>index a71f881..e35e478 100644
> >>--- a/hw/vfio/common.c
> >>+++ b/hw/vfio/common.c
> >>@@ -577,14 +577,18 @@ static int vfio_connect_container(VFIOGroup *group, 
> >>AddressSpace *as)
> >>
> >>          container->iommu_data.type1.initialized = true;
> >>
> >>-    } 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)) {
> >>+        bool v2 = !!ioctl(fd, VFIO_CHECK_EXTENSION, 
> >>VFIO_SPAPR_TCE_v2_IOMMU);
> >>+
> >>          ret = ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &fd);
> >>          if (ret) {
> >>              error_report("vfio: failed to set group container: %m");
> >>              ret = -errno;
> >>              goto free_container_exit;
> >>          }
> >>-        ret = ioctl(fd, VFIO_SET_IOMMU, VFIO_SPAPR_TCE_IOMMU);
> >>+        ret = ioctl(fd, VFIO_SET_IOMMU,
> >>+                v2 ? VFIO_SPAPR_TCE_v2_IOMMU : VFIO_SPAPR_TCE_IOMMU);
> >>          if (ret) {
> >>              error_report("vfio: failed to set iommu for container: %m");
> >>              ret = -errno;
> >>@@ -596,14 +600,20 @@ 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;
> >>+            }
> >>          }
> >>
> >>-        spapr_memory_listener_register(container);
> >>+        ret = spapr_memory_listener_register(container, v2 ? 2 : 1);
> >>+        if (ret) {
> >>+            error_report("vfio: RAM memory listener initialization failed 
> >>for container");
> >>+            goto listener_release_exit;
> >>+        }
> >>
> >>      } else {
> >>          error_report("vfio: No available IOMMU models");
> >>diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> >>index 5f79194..a670907 100644
> >>--- a/hw/vfio/spapr.c
> >>+++ b/hw/vfio/spapr.c
> >>@@ -17,6 +17,9 @@
> >>   *  along with this program; if not, see <http://www.gnu.org/licenses/>.
> >>   */
> >>
> >>+#include <sys/ioctl.h>
> >>+#include <linux/vfio.h>
> >>+
> >>  #include "hw/vfio/vfio-common.h"
> >>  #include "qemu/error-report.h"
> >>  #include "trace.h"
> >>@@ -211,16 +214,88 @@ static const MemoryListener 
> >>vfio_spapr_memory_listener = {
> >>      .region_del = vfio_spapr_listener_region_del,
> >>  };
> >>
> >>+static void vfio_ram_do_region(VFIOContainer *container,
> >>+                              MemoryRegionSection *section, unsigned long 
> >>req)
> >>+{
> >>+    int ret;
> >>+    struct vfio_iommu_spapr_register_memory reg = { .argsz = sizeof(reg) };
> >>+
> >>+    if (!memory_region_is_ram(section->mr) ||
> >>+        memory_region_is_skip_dump(section->mr)) {
> >>+        return;
> >>+    }
> >>+
> >>+    reg.vaddr = (__u64) memory_region_get_ram_ptr(section->mr) +
> >>+        section->offset_within_region;
> >
> >Is section->offset_within_region always page aligned?
> 
> 
> I think so as it is RAM. qemu_ram_alloc_from_file() and
> qemu_ram_alloc_internal() (called from memory_region_init_ram()) align.

Ok.  It just seems a but odd to me that offset is guaranteed page
aligned, but size is not.  An assert here might help to document the
assumptions you're making.

> >>+    reg.size = ROUND_UP(int128_get64(section->size), TARGET_PAGE_SIZE);
> >>+
> >>+    ret = ioctl(container->fd, req, &reg);
> >>+    trace_vfio_ram_register(_IOC_NR(req) - VFIO_BASE, reg.vaddr, reg.size, 
> >>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->iommu_data.spapr.ram_reg_initialized) {
> >>+        if (!container->iommu_data.spapr.ram_reg_error) {
> >>+            container->iommu_data.spapr.ram_reg_error = ret;
> >>+        }
> >
> >This is pretty clunky, but I don't immediately see a better way.
> >
> >Also.. won't the return value of ioctl() just be -1 on error, which
> >won't tell you much.  Do you want to store errno, instead?
> 
> Yes, I do, I'll fix it. Thanks.
> 
> 
> >>+    } else {
> >>+        hw_error("vfio: RAM registering failed, unable to continue");
> >>+    }
> >>+}
> >>+
> >>+static void vfio_spapr_ram_listener_region_add(MemoryListener *listener,
> >>+                                               MemoryRegionSection 
> >>*section)
> >>+{
> >>+    VFIOContainer *container = container_of(listener, VFIOContainer,
> >>+                                            iommu_data.spapr.ramlistener);
> >>+    memory_region_ref(section->mr);
> >>+    vfio_ram_do_region(container, section, 
> >>VFIO_IOMMU_SPAPR_REGISTER_MEMORY);
> >>+}
> >>+
> >>+static void vfio_spapr_ram_listener_region_del(MemoryListener *listener,
> >>+                                               MemoryRegionSection 
> >>*section)
> >>+{
> >>+    VFIOContainer *container = container_of(listener, VFIOContainer,
> >>+                                            iommu_data.spapr.ramlistener);
> >>+    memory_region_unref(section->mr);
> >>+    vfio_ram_do_region(container, section, 
> >>VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY);
> >>+}
> >>+
> >>+static const MemoryListener vfio_spapr_ram_memory_listener = {
> >>+    .region_add = vfio_spapr_ram_listener_region_add,
> >>+    .region_del = vfio_spapr_ram_listener_region_del,
> >>+};
> >>+
> >>  static void vfio_spapr_listener_release(VFIOContainer *container)
> >>  {
> >>      memory_listener_unregister(&container->iommu_data.spapr.listener);
> >>  }
> >>
> >>-void spapr_memory_listener_register(VFIOContainer *container)
> >>+static void vfio_spapr_listener_release_v2(VFIOContainer *container)
> >>+{
> >>+    memory_listener_unregister(&container->iommu_data.spapr.listener);
> >>+    vfio_spapr_listener_release(container);
> >>+}
> >>+
> >>+int spapr_memory_listener_register(VFIOContainer *container, int ver)
> >>  {
> >>      container->iommu_data.spapr.listener = vfio_spapr_memory_listener;
> >>      container->iommu_data.release = vfio_spapr_listener_release;
> >>-
> >>      memory_listener_register(&container->iommu_data.spapr.listener,
> >>                               container->space->as);
> >>+    if (ver < 2) {
> >>+        return 0;
> >>+    }
> >>+
> >>+    container->iommu_data.spapr.ramlistener = 
> >>vfio_spapr_ram_memory_listener;
> >>+    container->iommu_data.release = vfio_spapr_listener_release_v2;
> >>+    memory_listener_register(&container->iommu_data.spapr.ramlistener,
> >>+                             &address_space_memory);
> >>+
> >>+    container->iommu_data.spapr.ram_reg_initialized = true;
> >>+
> >>+    return container->iommu_data.spapr.ram_reg_error;
> >>  }
> >>diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> >>index d0b831c..b5ef446 100644
> >>--- a/include/hw/vfio/vfio-common.h
> >>+++ b/include/hw/vfio/vfio-common.h
> >>@@ -71,6 +71,9 @@ typedef struct VFIOType1 {
> >>
> >>  typedef struct VFIOSPAPR {
> >>      MemoryListener listener;
> >>+    MemoryListener ramlistener;
> >>+    int ram_reg_error;
> >>+    bool ram_reg_initialized;
> >>  } VFIOSPAPR;
> >>
> >>  typedef struct VFIOContainer {
> >>@@ -156,6 +159,6 @@ extern int vfio_dma_unmap(VFIOContainer *container,
> >>                            hwaddr iova, ram_addr_t size);
> >>  bool vfio_listener_skipped_section(MemoryRegionSection *section);
> >>
> >>-extern void spapr_memory_listener_register(VFIOContainer *container);
> >>+extern int spapr_memory_listener_register(VFIOContainer *container, int 
> >>ver);
> >>
> >>  #endif /* !HW_VFIO_VFIO_COMMON_H */
> >>diff --git a/trace-events b/trace-events
> >>index 1231ba4..2739140 100644
> >>--- a/trace-events
> >>+++ b/trace-events
> >>@@ -1563,6 +1563,7 @@ 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(int req, uint64_t va, uint64_t size, int ret) "req=%d 
> >>va=%"PRIx64" size=%"PRIx64" ret=%d"
> >>
> >>  #hw/acpi/memory_hotplug.c
> >>  mhp_acpi_invalid_slot_selected(uint32_t slot) "0x%"PRIx32
> >
> 
> 

-- 
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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