RE: [PATCH v4 05/12] vfio/iommufd: Introduce auto domain creation

[Duan, Zhenzhong]

>-----Original Message-----
>From: Joao Martins <joao.m.martins@oracle.com>
>Subject: [PATCH v4 05/12] vfio/iommufd: Introduce auto domain creation
>
>There's generally two modes of operation for IOMMUFD:
>
>* The simple user API which intends to perform relatively simple things
>with IOMMUs e.g. DPDK. It generally creates an IOAS and attach to VFIO
>and mainly performs IOAS_MAP and UNMAP.
>
>* The native IOMMUFD API where you have fine grained control of the
>IOMMU domain and model it accordingly. This is where most new feature
>are being steered to.
>
>For dirty tracking 2) is required, as it needs to ensure that
>the stage-2/parent IOMMU domain will only attach devices
>that support dirty tracking (so far it is all homogeneous in x86, likely
>not the case for smmuv3). Such invariant on dirty tracking provides a
>useful guarantee to VMMs that will refuse incompatible device
>attachments for IOMMU domains.
>
>Dirty tracking insurance is enforced via HWPT_ALLOC, which is
>responsible for creating an IOMMU domain. This is contrast to the
>'simple API' where the IOMMU domain is created by IOMMUFD
>automatically
>when it attaches to VFIO (usually referred as autodomains) but it has
>the needed handling for mdevs.
>
>To support dirty tracking with the advanced IOMMUFD API, it needs
>similar logic, where IOMMU domains are created and devices attached to
>compatible domains. Essentially mimmicing kernel
>iommufd_device_auto_get_domain(). With mdevs given there's no IOMMU
>domain
>it falls back to IOAS attach.
>
>The auto domain logic allows different IOMMU domains to be created when
>DMA dirty tracking is not desired (and VF can provide it), and others where
>it is. Here is not used in this way here given how VFIODevice migration
>state is initialized after the device attachment. But such mixed mode of
>IOMMU dirty tracking + device dirty tracking is an improvement that can
>be added on. Keep the 'all of nothing' of type1 approach that we have
>been using so far between container vs device dirty tracking.
>
>Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>---
> include/hw/vfio/vfio-common.h |  9 ++++
> include/sysemu/iommufd.h      |  5 +++
> backends/iommufd.c            | 30 +++++++++++++
> hw/vfio/iommufd.c             | 82
>+++++++++++++++++++++++++++++++++++
> backends/trace-events         |  1 +
> 5 files changed, 127 insertions(+)
>
>diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-
>common.h
>index 7419466bca92..2dd468ce3c02 100644
>--- a/include/hw/vfio/vfio-common.h
>+++ b/include/hw/vfio/vfio-common.h
>@@ -95,10 +95,17 @@ typedef struct VFIOHostDMAWindow {
>
> typedef struct IOMMUFDBackend IOMMUFDBackend;
>
>+typedef struct VFIOIOASHwpt {
>+    uint32_t hwpt_id;
>+    QLIST_HEAD(, VFIODevice) device_list;
>+    QLIST_ENTRY(VFIOIOASHwpt) next;
>+} VFIOIOASHwpt;
>+
> typedef struct VFIOIOMMUFDContainer {
>     VFIOContainerBase bcontainer;
>     IOMMUFDBackend *be;
>     uint32_t ioas_id;
>+    QLIST_HEAD(, VFIOIOASHwpt) hwpt_list;
> } VFIOIOMMUFDContainer;
>
> OBJECT_DECLARE_SIMPLE_TYPE(VFIOIOMMUFDContainer,
>VFIO_IOMMU_IOMMUFD);
>@@ -135,6 +142,8 @@ typedef struct VFIODevice {
>     HostIOMMUDevice *hiod;
>     int devid;
>     IOMMUFDBackend *iommufd;
>+    VFIOIOASHwpt *hwpt;
>+    QLIST_ENTRY(VFIODevice) hwpt_next;
> } VFIODevice;
>
> struct VFIODeviceOps {
>diff --git a/include/sysemu/iommufd.h b/include/sysemu/iommufd.h
>index 57d502a1c79a..e917e7591d05 100644
>--- a/include/sysemu/iommufd.h
>+++ b/include/sysemu/iommufd.h
>@@ -50,6 +50,11 @@ int
>iommufd_backend_unmap_dma(IOMMUFDBackend *be, uint32_t ioas_id,
> bool iommufd_backend_get_device_info(IOMMUFDBackend *be, uint32_t
>devid,
>                                      uint32_t *type, void *data, uint32_t len,
>                                      uint64_t *caps, Error **errp);
>+bool iommufd_backend_alloc_hwpt(IOMMUFDBackend *be, uint32_t
>dev_id,
>+                                uint32_t pt_id, uint32_t flags,
>+                                uint32_t data_type, uint32_t data_len,
>+                                void *data_ptr, uint32_t *out_hwpt,
>+                                Error **errp);
>
> #define TYPE_HOST_IOMMU_DEVICE_IOMMUFD
>TYPE_HOST_IOMMU_DEVICE "-iommufd"
> #endif
>diff --git a/backends/iommufd.c b/backends/iommufd.c
>index 2b3d51af26d2..5d3dfa917415 100644
>--- a/backends/iommufd.c
>+++ b/backends/iommufd.c
>@@ -208,6 +208,36 @@ int
>iommufd_backend_unmap_dma(IOMMUFDBackend *be, uint32_t ioas_id,
>     return ret;
> }
>
>+bool iommufd_backend_alloc_hwpt(IOMMUFDBackend *be, uint32_t
>dev_id,
>+                                uint32_t pt_id, uint32_t flags,
>+                                uint32_t data_type, uint32_t data_len,
>+                                void *data_ptr, uint32_t *out_hwpt,
>+                                Error **errp)
>+{
>+    int ret, fd = be->fd;
>+    struct iommu_hwpt_alloc alloc_hwpt = {
>+        .size = sizeof(struct iommu_hwpt_alloc),
>+        .flags = flags,
>+        .dev_id = dev_id,
>+        .pt_id = pt_id,
>+        .data_type = data_type,
>+        .data_len = data_len,
>+        .data_uptr = (uint64_t)data_ptr,
>+    };
>+
>+    ret = ioctl(fd, IOMMU_HWPT_ALLOC, &alloc_hwpt);
>+    trace_iommufd_backend_alloc_hwpt(fd, dev_id, pt_id, flags, data_type,
>+                                     data_len, (uint64_t)data_ptr,
>+                                     alloc_hwpt.out_hwpt_id, ret);
>+    if (ret) {
>+        error_setg_errno(errp, errno, "Failed to allocate hwpt");
>+        return false;
>+    }
>+
>+    *out_hwpt = alloc_hwpt.out_hwpt_id;
>+    return true;
>+}
>+
> bool iommufd_backend_get_device_info(IOMMUFDBackend *be, uint32_t
>devid,
>                                      uint32_t *type, void *data, uint32_t len,
>                                      uint64_t *caps, Error **errp)
>diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
>index 077dea8f1b64..325c7598d5a1 100644
>--- a/hw/vfio/iommufd.c
>+++ b/hw/vfio/iommufd.c
>@@ -212,10 +212,86 @@ static bool
>iommufd_cdev_detach_ioas_hwpt(VFIODevice *vbasedev, Error **errp)
>     return true;
> }
>
>+static bool iommufd_cdev_autodomains_get(VFIODevice *vbasedev,
>+                                         VFIOIOMMUFDContainer *container,
>+                                         Error **errp)
>+{
>+    IOMMUFDBackend *iommufd = vbasedev->iommufd;
>+    uint32_t flags = 0;
>+    VFIOIOASHwpt *hwpt;
>+    uint32_t hwpt_id;
>+    int ret;
>+
>+    /* Try to find a domain */
>+    QLIST_FOREACH(hwpt, &container->hwpt_list, next) {
>+        ret = iommufd_cdev_attach_ioas_hwpt(vbasedev, hwpt->hwpt_id,
>errp);

If there is already an hwpt that supports dirty tracking.
Another device that doesn't support dirty tracking attaches to this hwpt, will 
it succeed?

If existing hwpt doesn't support dirty tracking.
Another device supporting dirty tracking attaches to that hwpt, what will 
happen?

Thanks
Zhenzhong

>+        if (ret) {
>+            /* -EINVAL means the domain is incompatible with the device. */
>+            if (ret == -EINVAL) {
>+                /*
>+                 * It is an expected failure and it just means we will try
>+                 * another domain, or create one if no existing compatible
>+                 * domain is found. Hence why the error is discarded below.
>+                 */
>+                error_free(*errp);
>+                *errp = NULL;
>+                continue;
>+            }
>+
>+            return false;
>+        } else {
>+            vbasedev->hwpt = hwpt;
>+            QLIST_INSERT_HEAD(&hwpt->device_list, vbasedev, hwpt_next);
>+            return true;
>+        }
>+    }
>+
>+    if (!iommufd_backend_alloc_hwpt(iommufd, vbasedev->devid,
>+                                    container->ioas_id, flags,
>+                                    IOMMU_HWPT_DATA_NONE, 0, NULL,
>+                                    &hwpt_id, errp)) {
>+        return false;
>+    }
>+
>+    hwpt = g_malloc0(sizeof(*hwpt));
>+    hwpt->hwpt_id = hwpt_id;
>+    QLIST_INIT(&hwpt->device_list);
>+
>+    ret = iommufd_cdev_attach_ioas_hwpt(vbasedev, hwpt->hwpt_id, errp);
>+    if (ret) {
>+        iommufd_backend_free_id(container->be, hwpt->hwpt_id);
>+        g_free(hwpt);
>+        return false;
>+    }
>+
>+    vbasedev->hwpt = hwpt;
>+    QLIST_INSERT_HEAD(&hwpt->device_list, vbasedev, hwpt_next);
>+    QLIST_INSERT_HEAD(&container->hwpt_list, hwpt, next);
>+    return true;
>+}
>+
>+static void iommufd_cdev_autodomains_put(VFIODevice *vbasedev,
>+                                         VFIOIOMMUFDContainer *container)
>+{
>+    VFIOIOASHwpt *hwpt = vbasedev->hwpt;
>+
>+    QLIST_REMOVE(vbasedev, hwpt_next);
>+    if (QLIST_EMPTY(&hwpt->device_list)) {
>+        QLIST_REMOVE(hwpt, next);
>+        iommufd_backend_free_id(container->be, hwpt->hwpt_id);
>+        g_free(hwpt);
>+    }
>+}
>+
> static bool iommufd_cdev_attach_container(VFIODevice *vbasedev,
>                                           VFIOIOMMUFDContainer *container,
>                                           Error **errp)
> {
>+    /* mdevs aren't physical devices and will fail with auto domains */
>+    if (!vbasedev->mdev) {
>+        return iommufd_cdev_autodomains_get(vbasedev, container, errp);
>+    }
>+
>     return !iommufd_cdev_attach_ioas_hwpt(vbasedev, container->ioas_id,
>errp);
> }
>
>@@ -224,6 +300,11 @@ static void
>iommufd_cdev_detach_container(VFIODevice *vbasedev,
> {
>     Error *err = NULL;
>
>+    if (vbasedev->hwpt) {
>+        iommufd_cdev_autodomains_put(vbasedev, container);
>+        return;
>+    }
>+
>     if (!iommufd_cdev_detach_ioas_hwpt(vbasedev, &err)) {
>         error_report_err(err);
>     }
>@@ -354,6 +435,7 @@ static bool iommufd_cdev_attach(const char *name,
>VFIODevice *vbasedev,
>     container =
>VFIO_IOMMU_IOMMUFD(object_new(TYPE_VFIO_IOMMU_IOMMUFD));
>     container->be = vbasedev->iommufd;
>     container->ioas_id = ioas_id;
>+    QLIST_INIT(&container->hwpt_list);
>
>     bcontainer = &container->bcontainer;
>     vfio_address_space_insert(space, bcontainer);
>diff --git a/backends/trace-events b/backends/trace-events
>index 211e6f374adc..4d8ac02fe7d6 100644
>--- a/backends/trace-events
>+++ b/backends/trace-events
>@@ -14,4 +14,5 @@ iommufd_backend_map_dma(int iommufd, uint32_t
>ioas, uint64_t iova, uint64_t size
> iommufd_backend_unmap_dma_non_exist(int iommufd, uint32_t ioas,
>uint64_t iova, uint64_t size, int ret) " Unmap nonexistent mapping:
>iommufd=%d ioas=%d iova=0x%"PRIx64" size=0x%"PRIx64" (%d)"
> iommufd_backend_unmap_dma(int iommufd, uint32_t ioas, uint64_t iova,
>uint64_t size, int ret) " iommufd=%d ioas=%d iova=0x%"PRIx64"
>size=0x%"PRIx64" (%d)"
> iommufd_backend_alloc_ioas(int iommufd, uint32_t ioas) " iommufd=%d
>ioas=%d"
>+iommufd_backend_alloc_hwpt(int iommufd, uint32_t dev_id, uint32_t
>pt_id, uint32_t flags, uint32_t hwpt_type, uint32_t len, uint64_t data_ptr,
>uint32_t out_hwpt_id, int ret) " iommufd=%d dev_id=%u pt_id=%u
>flags=0x%x hwpt_type=%u len=%u data_ptr=0x%"PRIx64" out_hwpt=%u
>(%d)"
> iommufd_backend_free_id(int iommufd, uint32_t id, int ret) " iommufd=%d
>id=%d (%d)"
>--
>2.17.2