[PATCH v6 0/2] vhost-vdpa: add support for vIOMMU

[PATCH v6 0/2] vhost-vdpa: add support for vIOMMU

[Cindy Lu]

changes in V3
1. Move function vfio_get_xlat_addr to memory.c
2. Use the existing memory listener, while the MR is
iommu MR then call the function iommu_region_add/
iommu_region_del

changes in V4
1.make the comments in vfio_get_xlat_addr more general

changes in V5
1. Address the comments in the last version
2. Add a new arg in the function vfio_get_xlat_addr, which shows whether
the memory is backed by a discard manager. So the device can have its
own warning.

changes in V6
move the error_report for the unpopulated discard back to
memeory_get_xlat_add

Cindy Lu (2):
  vfio: move function vfio_get_xlat_addr() to memory.c
  vhost-vdpa: add support for vIOMMU

 hw/vfio/common.c               | 135 +++++++++++----------------------
 hw/virtio/vhost-vdpa.c         | 123 +++++++++++++++++++++++++++---
 include/exec/memory.h          |   4 +
 include/hw/virtio/vhost-vdpa.h |  10 +++
 softmmu/memory.c               |  72 ++++++++++++++++++
 5 files changed, 244 insertions(+), 100 deletions(-)

-- 
2.34.3

[PATCH v6 1/2] vfio: move function vfio_get_xlat_addr() to memory.c

[Cindy Lu]

- Move the function vfio_get_xlat_addr to softmmu/memory.c, and
  change the name to memory_get_xlat_addr(). So we can use this
  function on other devices, such as vDPA device.
- Add a new bool arg in this function, which shows whether the memory is
  backed by a discard manager. So the device can have its own warning.

Signed-off-by: Cindy Lu <lulu@redhat.com>
---
 hw/vfio/common.c      | 135 ++++++++++++++----------------------------
 include/exec/memory.h |   4 ++
 softmmu/memory.c      |  72 ++++++++++++++++++++++
 3 files changed, 122 insertions(+), 89 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index ace9562a9b..06ebbb82c7 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -574,92 +574,6 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section)
            section->offset_within_address_space & (1ULL << 63);
 }
 
-/* Called with rcu_read_lock held.  */
-static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
-                               ram_addr_t *ram_addr, bool *read_only)
-{
-    MemoryRegion *mr;
-    hwaddr xlat;
-    hwaddr len = iotlb->addr_mask + 1;
-    bool writable = iotlb->perm & IOMMU_WO;
-
-    /*
-     * The IOMMU TLB entry we have just covers translation through
-     * this IOMMU to its immediate target.  We need to translate
-     * it the rest of the way through to memory.
-     */
-    mr = address_space_translate(&address_space_memory,
-                                 iotlb->translated_addr,
-                                 &xlat, &len, writable,
-                                 MEMTXATTRS_UNSPECIFIED);
-    if (!memory_region_is_ram(mr)) {
-        error_report("iommu map to non memory area %"HWADDR_PRIx"",
-                     xlat);
-        return false;
-    } else if (memory_region_has_ram_discard_manager(mr)) {
-        RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr);
-        MemoryRegionSection tmp = {
-            .mr = mr,
-            .offset_within_region = xlat,
-            .size = int128_make64(len),
-        };
-
-        /*
-         * Malicious VMs can map memory into the IOMMU, which is expected
-         * to remain discarded. vfio will pin all pages, populating memory.
-         * Disallow that. vmstate priorities make sure any RamDiscardManager
-         * were already restored before IOMMUs are restored.
-         */
-        if (!ram_discard_manager_is_populated(rdm, &tmp)) {
-            error_report("iommu map to discarded memory (e.g., unplugged via"
-                         " virtio-mem): %"HWADDR_PRIx"",
-                         iotlb->translated_addr);
-            return false;
-        }
-
-        /*
-         * Malicious VMs might trigger discarding of IOMMU-mapped memory. The
-         * pages will remain pinned inside vfio until unmapped, resulting in a
-         * higher memory consumption than expected. If memory would get
-         * populated again later, there would be an inconsistency between pages
-         * pinned by vfio and pages seen by QEMU. This is the case until
-         * unmapped from the IOMMU (e.g., during device reset).
-         *
-         * With malicious guests, we really only care about pinning more memory
-         * than expected. RLIMIT_MEMLOCK set for the user/process can never be
-         * exceeded and can be used to mitigate this problem.
-         */
-        warn_report_once("Using vfio with vIOMMUs and coordinated discarding of"
-                         " RAM (e.g., virtio-mem) works, however, malicious"
-                         " guests can trigger pinning of more memory than"
-                         " intended via an IOMMU. It's possible to mitigate "
-                         " by setting/adjusting RLIMIT_MEMLOCK.");
-    }
-
-    /*
-     * Translation truncates length to the IOMMU page size,
-     * check that it did not truncate too much.
-     */
-    if (len & iotlb->addr_mask) {
-        error_report("iommu has granularity incompatible with target AS");
-        return false;
-    }
-
-    if (vaddr) {
-        *vaddr = memory_region_get_ram_ptr(mr) + xlat;
-    }
-
-    if (ram_addr) {
-        *ram_addr = memory_region_get_ram_addr(mr) + xlat;
-    }
-
-    if (read_only) {
-        *read_only = !writable || mr->readonly;
-    }
-
-    return true;
-}
-
 static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
 {
     VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n);
@@ -681,10 +595,32 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
 
     if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) {
         bool read_only;
+        bool mr_has_discard_manager;
 
-        if (!vfio_get_xlat_addr(iotlb, &vaddr, NULL, &read_only)) {
+        if (!memory_get_xlat_addr(iotlb, &vaddr, NULL, &read_only,
+                                  &mr_has_discard_manager)) {
             goto out;
         }
+        if (mr_has_discard_manager) {
+            /*
+             * Malicious VMs might trigger discarding of IOMMU-mapped memory.
+             * The pages will remain pinned inside vfio until unmapped,
+             * resulting in a higher memory consumption than expected. If memory
+             * would get populated again later, there would be an inconsistency
+             * between pages pinned by vfio and pages seen by QEMU. This is the
+             * case until unmapped from the IOMMU (e.g., during device reset).
+             *
+             * With malicious guests, we really only care about pinning more
+             * memory than expected. RLIMIT_MEMLOCK set for the user/process can
+             * never be exceeded and can be used to mitigate this problem.
+             */
+            warn_report_once(
+                "Using vfio with vIOMMUs and coordinated discarding of"
+                " RAM (e.g., virtio-mem) works, however, malicious"
+                " guests can trigger pinning of more memory than"
+                " intended via an IOMMU. It's possible to mitigate "
+                " by setting/adjusting RLIMIT_MEMLOCK.");
+        }
         /*
          * vaddr is only valid until rcu_read_unlock(). But after
          * vfio_dma_map has set up the mapping the pages will be
@@ -1349,6 +1285,7 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
     VFIOContainer *container = giommu->container;
     hwaddr iova = iotlb->iova + giommu->iommu_offset;
     ram_addr_t translated_addr;
+    bool mr_has_discard_manager;
 
     trace_vfio_iommu_map_dirty_notify(iova, iova + iotlb->addr_mask);
 
@@ -1359,9 +1296,9 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
     }
 
     rcu_read_lock();
-    if (vfio_get_xlat_addr(iotlb, NULL, &translated_addr, NULL)) {
+    if (memory_get_xlat_addr(iotlb, NULL, &translated_addr, NULL,
+                             &mr_has_discard_manager)) {
         int ret;
-
         ret = vfio_get_dirty_bitmap(container, iova, iotlb->addr_mask + 1,
                                     translated_addr);
         if (ret) {
@@ -1370,6 +1307,26 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
                          container, iova,
                          iotlb->addr_mask + 1, ret);
         }
+        if (mr_has_discard_manager) {
+            /*
+             * Malicious VMs might trigger discarding of IOMMU-mapped memory.
+             * The pages will remain pinned inside vfio until unmapped,
+             * resulting in a higher memory consumption than expected. If memory
+             * would get populated again later, there would be an inconsistency
+             * between pages pinned by vfio and pages seen by QEMU. This is the
+             * case until unmapped from the IOMMU (e.g., during device reset).
+             *
+             * With malicious guests, we really only care about pinning more
+             * memory than expected. RLIMIT_MEMLOCK set for the user/process can
+             * never be exceeded and can be used to mitigate this problem.
+             */
+            warn_report_once(
+                "Using vfio with vIOMMUs and coordinated discarding of"
+                " RAM (e.g., virtio-mem) works, however, malicious"
+                " guests can trigger pinning of more memory than"
+                " intended via an IOMMU. It's possible to mitigate "
+                " by setting/adjusting RLIMIT_MEMLOCK.");
+        }
     }
     rcu_read_unlock();
 }
diff --git a/include/exec/memory.h b/include/exec/memory.h
index bfb1de8eea..d1e79c39dc 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -713,6 +713,10 @@ void ram_discard_manager_register_listener(RamDiscardManager *rdm,
 void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
                                              RamDiscardListener *rdl);
 
+bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
+                          ram_addr_t *ram_addr, bool *read_only,
+                          bool *mr_has_discard_manager);
+
 typedef struct CoalescedMemoryRange CoalescedMemoryRange;
 typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd;
 
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 7ba2048836..bc0be3f62c 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -33,6 +33,7 @@
 #include "qemu/accel.h"
 #include "hw/boards.h"
 #include "migration/vmstate.h"
+#include "exec/address-spaces.h"
 
 //#define DEBUG_UNASSIGNED
 
@@ -2121,6 +2122,77 @@ void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
     rdmc->unregister_listener(rdm, rdl);
 }
 
+/* Called with rcu_read_lock held.  */
+bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
+                          ram_addr_t *ram_addr, bool *read_only,
+                          bool *mr_has_discard_manager)
+{
+    MemoryRegion *mr;
+    hwaddr xlat;
+    hwaddr len = iotlb->addr_mask + 1;
+    bool writable = iotlb->perm & IOMMU_WO;
+
+    if (mr_has_discard_manager) {
+        *mr_has_discard_manager = false;
+    }
+    /*
+     * The IOMMU TLB entry we have just covers translation through
+     * this IOMMU to its immediate target.  We need to translate
+     * it the rest of the way through to memory.
+     */
+    mr = address_space_translate(&address_space_memory, iotlb->translated_addr,
+                                 &xlat, &len, writable, MEMTXATTRS_UNSPECIFIED);
+    if (!memory_region_is_ram(mr)) {
+        error_report("iommu map to non memory area %" HWADDR_PRIx "", xlat);
+        return false;
+    } else if (memory_region_has_ram_discard_manager(mr)) {
+        RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr);
+        MemoryRegionSection tmp = {
+            .mr = mr,
+            .offset_within_region = xlat,
+            .size = int128_make64(len),
+        };
+        if (mr_has_discard_manager) {
+            *mr_has_discard_manager = true;
+        }
+        /*
+         * Malicious VMs can map memory into the IOMMU, which is expected
+         * to remain discarded. vfio will pin all pages, populating memory.
+         * Disallow that. vmstate priorities make sure any RamDiscardManager
+         * were already restored before IOMMUs are restored.
+         */
+        if (!ram_discard_manager_is_populated(rdm, &tmp)) {
+            error_report("iommu map to discarded memory (e.g., unplugged via"
+                         " virtio-mem): %" HWADDR_PRIx "",
+                         iotlb->translated_addr);
+            return false;
+        }
+    }
+
+    /*
+     * Translation truncates length to the IOMMU page size,
+     * check that it did not truncate too much.
+     */
+    if (len & iotlb->addr_mask) {
+        error_report("iommu has granularity incompatible with target AS");
+        return false;
+    }
+
+    if (vaddr) {
+        *vaddr = memory_region_get_ram_ptr(mr) + xlat;
+    }
+
+    if (ram_addr) {
+        *ram_addr = memory_region_get_ram_addr(mr) + xlat;
+    }
+
+    if (read_only) {
+        *read_only = !writable || mr->readonly;
+    }
+
+    return true;
+}
+
 void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
 {
     uint8_t mask = 1 << client;
-- 
2.34.3

[PATCH v6 2/2] vhost-vdpa: add support for vIOMMU

[Cindy Lu]

Add support for vIOMMU. add the new function to deal with iommu MR.
- during iommu_region_add register a specific IOMMU notifier,
 and store all notifiers in a list.
- during iommu_region_del, compare and delete the IOMMU notifier from the list

Verified in vp_vdpa and vdpa_sim_net driver

Signed-off-by: Cindy Lu <lulu@redhat.com>
---
 hw/virtio/vhost-vdpa.c         | 123 ++++++++++++++++++++++++++++++---
 include/hw/virtio/vhost-vdpa.h |  10 +++
 2 files changed, 122 insertions(+), 11 deletions(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 3ff9ce3501..dcfaaccfa9 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -26,6 +26,7 @@
 #include "cpu.h"
 #include "trace.h"
 #include "qapi/error.h"
+#include "hw/virtio/virtio-access.h"
 
 /*
  * Return one past the end of the end of section. Be careful with uint64_t
@@ -44,7 +45,6 @@ static bool vhost_vdpa_listener_skipped_section(MemoryRegionSection *section,
                                                 uint64_t iova_min,
                                                 uint64_t iova_max)
 {
-    Int128 llend;
 
     if ((!memory_region_is_ram(section->mr) &&
          !memory_region_is_iommu(section->mr)) ||
@@ -61,14 +61,6 @@ static bool vhost_vdpa_listener_skipped_section(MemoryRegionSection *section,
         return true;
     }
 
-    llend = vhost_vdpa_section_end(section);
-    if (int128_gt(llend, int128_make64(iova_max))) {
-        error_report("RAM section out of device range (max=0x%" PRIx64
-                     ", end addr=0x%" PRIx64 ")",
-                     iova_max, int128_get64(llend));
-        return true;
-    }
-
     return false;
 }
 
@@ -173,6 +165,106 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
     v->iotlb_batch_begin_sent = false;
 }
 
+static void vhost_vdpa_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
+{
+    struct vdpa_iommu *iommu = container_of(n, struct vdpa_iommu, n);
+
+    hwaddr iova = iotlb->iova + iommu->iommu_offset;
+    struct vhost_vdpa *v = iommu->dev;
+    void *vaddr;
+    int ret;
+
+    if (iotlb->target_as != &address_space_memory) {
+        error_report("Wrong target AS \"%s\", only system memory is allowed",
+                     iotlb->target_as->name ? iotlb->target_as->name : "none");
+        return;
+    }
+    RCU_READ_LOCK_GUARD();
+    vhost_vdpa_iotlb_batch_begin_once(v);
+
+    if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) {
+        bool read_only;
+
+        if (!memory_get_xlat_addr(iotlb, &vaddr, NULL, &read_only, NULL)) {
+            return;
+        }
+        ret =
+            vhost_vdpa_dma_map(v, iova, iotlb->addr_mask + 1, vaddr, read_only);
+        if (ret) {
+            error_report("vhost_vdpa_dma_map(%p, 0x%" HWADDR_PRIx ", "
+                         "0x%" HWADDR_PRIx ", %p) = %d (%m)",
+                         v, iova, iotlb->addr_mask + 1, vaddr, ret);
+        }
+    } else {
+        ret = vhost_vdpa_dma_unmap(v, iova, iotlb->addr_mask + 1);
+        if (ret) {
+            error_report("vhost_vdpa_dma_unmap(%p, 0x%" HWADDR_PRIx ", "
+                         "0x%" HWADDR_PRIx ") = %d (%m)",
+                         v, iova, iotlb->addr_mask + 1, ret);
+        }
+    }
+}
+
+static void vhost_vdpa_iommu_region_add(MemoryListener *listener,
+                                        MemoryRegionSection *section)
+{
+    struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
+
+    struct vdpa_iommu *iommu;
+    Int128 end;
+    int iommu_idx;
+    IOMMUMemoryRegion *iommu_mr;
+    int ret;
+
+    iommu_mr = IOMMU_MEMORY_REGION(section->mr);
+
+    iommu = g_malloc0(sizeof(*iommu));
+    end =  int128_add(int128_make64(section->offset_within_region),
+            section->size);
+    end = int128_sub(end, int128_one());
+    iommu_idx = memory_region_iommu_attrs_to_index(iommu_mr,
+            MEMTXATTRS_UNSPECIFIED);
+
+    iommu->iommu_mr = iommu_mr;
+
+    iommu_notifier_init(
+        &iommu->n, vhost_vdpa_iommu_map_notify, IOMMU_NOTIFIER_IOTLB_EVENTS,
+        section->offset_within_region, int128_get64(end), iommu_idx);
+    iommu->iommu_offset =
+        section->offset_within_address_space - section->offset_within_region;
+    iommu->dev = v;
+
+    ret = memory_region_register_iommu_notifier(section->mr, &iommu->n, NULL);
+    if (ret) {
+        g_free(iommu);
+        return;
+    }
+
+    QLIST_INSERT_HEAD(&v->iommu_list, iommu, iommu_next);
+    memory_region_iommu_replay(iommu->iommu_mr, &iommu->n);
+
+    return;
+}
+
+static void vhost_vdpa_iommu_region_del(MemoryListener *listener,
+                                        MemoryRegionSection *section)
+{
+    struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
+
+    struct vdpa_iommu *iommu;
+
+    QLIST_FOREACH(iommu, &v->iommu_list, iommu_next)
+    {
+        if (MEMORY_REGION(iommu->iommu_mr) == section->mr &&
+            iommu->n.start == section->offset_within_region) {
+            memory_region_unregister_iommu_notifier(section->mr, &iommu->n);
+            QLIST_REMOVE(iommu, iommu_next);
+            g_free(iommu);
+            break;
+        }
+    }
+}
+
 static void vhost_vdpa_listener_region_add(MemoryListener *listener,
                                            MemoryRegionSection *section)
 {
@@ -186,6 +278,10 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
                                             v->iova_range.last)) {
         return;
     }
+    if (memory_region_is_iommu(section->mr)) {
+        vhost_vdpa_iommu_region_add(listener, section);
+        return;
+    }
 
     if (unlikely((section->offset_within_address_space & ~TARGET_PAGE_MASK) !=
                  (section->offset_within_region & ~TARGET_PAGE_MASK))) {
@@ -260,6 +356,10 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
                                             v->iova_range.last)) {
         return;
     }
+    if (memory_region_is_iommu(section->mr)) {
+        vhost_vdpa_iommu_region_del(listener, section);
+        return;
+    }
 
     if (unlikely((section->offset_within_address_space & ~TARGET_PAGE_MASK) !=
                  (section->offset_within_region & ~TARGET_PAGE_MASK))) {
@@ -312,6 +412,7 @@ static const MemoryListener vhost_vdpa_memory_listener = {
     .region_del = vhost_vdpa_listener_region_del,
 };
 
+
 static int vhost_vdpa_call(struct vhost_dev *dev, unsigned long int request,
                              void *arg)
 {
@@ -587,7 +688,6 @@ static int vhost_vdpa_cleanup(struct vhost_dev *dev)
     v = dev->opaque;
     trace_vhost_vdpa_cleanup(dev, v);
     vhost_vdpa_host_notifiers_uninit(dev, dev->nvqs);
-    memory_listener_unregister(&v->listener);
     vhost_vdpa_svq_cleanup(dev);
 
     dev->opaque = NULL;
@@ -1127,7 +1227,8 @@ static int vhost_vdpa_dev_start(struct vhost_dev *dev, bool started)
     }
 
     if (started) {
-        memory_listener_register(&v->listener, &address_space_memory);
+        memory_listener_register(&v->listener, dev->vdev->dma_as);
+
         return vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
     } else {
         vhost_vdpa_reset_device(dev);
diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index d10a89303e..64a46e37cb 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -41,8 +41,18 @@ typedef struct vhost_vdpa {
     void *shadow_vq_ops_opaque;
     struct vhost_dev *dev;
     VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX];
+    QLIST_HEAD(, vdpa_iommu) iommu_list;
+    IOMMUNotifier n;
 } VhostVDPA;
 
+struct vdpa_iommu {
+    struct vhost_vdpa *dev;
+    IOMMUMemoryRegion *iommu_mr;
+    hwaddr iommu_offset;
+    IOMMUNotifier n;
+    QLIST_ENTRY(vdpa_iommu) iommu_next;
+};
+
 int vhost_vdpa_dma_map(struct vhost_vdpa *v, hwaddr iova, hwaddr size,
                        void *vaddr, bool readonly);
 int vhost_vdpa_dma_unmap(struct vhost_vdpa *v, hwaddr iova, hwaddr size);
-- 
2.34.3

Re: [PATCH v6 1/2] vfio: move function vfio_get_xlat_addr() to memory.c

[Alex Williamson]

On Sun, 30 Oct 2022 14:01:05 +0800
Cindy Lu <lulu@redhat.com> wrote:

> - Move the function vfio_get_xlat_addr to softmmu/memory.c, and
>   change the name to memory_get_xlat_addr(). So we can use this
>   function on other devices, such as vDPA device.
> - Add a new bool arg in this function, which shows whether the memory is
>   backed by a discard manager. So the device can have its own warning.
> 
> Signed-off-by: Cindy Lu <lulu@redhat.com>
> ---
>  hw/vfio/common.c      | 135 ++++++++++++++----------------------------
>  include/exec/memory.h |   4 ++
>  softmmu/memory.c      |  72 ++++++++++++++++++++++
>  3 files changed, 122 insertions(+), 89 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index ace9562a9b..06ebbb82c7 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -574,92 +574,6 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section)
>             section->offset_within_address_space & (1ULL << 63);
>  }
>  
> -/* Called with rcu_read_lock held.  */
> -static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> -                               ram_addr_t *ram_addr, bool *read_only)
> -{
> -    MemoryRegion *mr;
> -    hwaddr xlat;
> -    hwaddr len = iotlb->addr_mask + 1;
> -    bool writable = iotlb->perm & IOMMU_WO;
> -
> -    /*
> -     * The IOMMU TLB entry we have just covers translation through
> -     * this IOMMU to its immediate target.  We need to translate
> -     * it the rest of the way through to memory.
> -     */
> -    mr = address_space_translate(&address_space_memory,
> -                                 iotlb->translated_addr,
> -                                 &xlat, &len, writable,
> -                                 MEMTXATTRS_UNSPECIFIED);
> -    if (!memory_region_is_ram(mr)) {
> -        error_report("iommu map to non memory area %"HWADDR_PRIx"",
> -                     xlat);
> -        return false;
> -    } else if (memory_region_has_ram_discard_manager(mr)) {
> -        RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr);
> -        MemoryRegionSection tmp = {
> -            .mr = mr,
> -            .offset_within_region = xlat,
> -            .size = int128_make64(len),
> -        };
> -
> -        /*
> -         * Malicious VMs can map memory into the IOMMU, which is expected
> -         * to remain discarded. vfio will pin all pages, populating memory.
> -         * Disallow that. vmstate priorities make sure any RamDiscardManager
> -         * were already restored before IOMMUs are restored.
> -         */
> -        if (!ram_discard_manager_is_populated(rdm, &tmp)) {
> -            error_report("iommu map to discarded memory (e.g., unplugged via"
> -                         " virtio-mem): %"HWADDR_PRIx"",
> -                         iotlb->translated_addr);
> -            return false;
> -        }
> -
> -        /*
> -         * Malicious VMs might trigger discarding of IOMMU-mapped memory. The
> -         * pages will remain pinned inside vfio until unmapped, resulting in a
> -         * higher memory consumption than expected. If memory would get
> -         * populated again later, there would be an inconsistency between pages
> -         * pinned by vfio and pages seen by QEMU. This is the case until
> -         * unmapped from the IOMMU (e.g., during device reset).
> -         *
> -         * With malicious guests, we really only care about pinning more memory
> -         * than expected. RLIMIT_MEMLOCK set for the user/process can never be
> -         * exceeded and can be used to mitigate this problem.
> -         */
> -        warn_report_once("Using vfio with vIOMMUs and coordinated discarding of"
> -                         " RAM (e.g., virtio-mem) works, however, malicious"
> -                         " guests can trigger pinning of more memory than"
> -                         " intended via an IOMMU. It's possible to mitigate "
> -                         " by setting/adjusting RLIMIT_MEMLOCK.");
> -    }
> -
> -    /*
> -     * Translation truncates length to the IOMMU page size,
> -     * check that it did not truncate too much.
> -     */
> -    if (len & iotlb->addr_mask) {
> -        error_report("iommu has granularity incompatible with target AS");
> -        return false;
> -    }
> -
> -    if (vaddr) {
> -        *vaddr = memory_region_get_ram_ptr(mr) + xlat;
> -    }
> -
> -    if (ram_addr) {
> -        *ram_addr = memory_region_get_ram_addr(mr) + xlat;
> -    }
> -
> -    if (read_only) {
> -        *read_only = !writable || mr->readonly;
> -    }
> -
> -    return true;
> -}
> -
>  static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>  {
>      VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n);
> @@ -681,10 +595,32 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>  
>      if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) {
>          bool read_only;
> +        bool mr_has_discard_manager;
>  
> -        if (!vfio_get_xlat_addr(iotlb, &vaddr, NULL, &read_only)) {
> +        if (!memory_get_xlat_addr(iotlb, &vaddr, NULL, &read_only,
> +                                  &mr_has_discard_manager)) {
>              goto out;
>          }
> +        if (mr_has_discard_manager) {
> +            /*
> +             * Malicious VMs might trigger discarding of IOMMU-mapped memory.
> +             * The pages will remain pinned inside vfio until unmapped,
> +             * resulting in a higher memory consumption than expected. If memory
> +             * would get populated again later, there would be an inconsistency
> +             * between pages pinned by vfio and pages seen by QEMU. This is the
> +             * case until unmapped from the IOMMU (e.g., during device reset).
> +             *
> +             * With malicious guests, we really only care about pinning more
> +             * memory than expected. RLIMIT_MEMLOCK set for the user/process can
> +             * never be exceeded and can be used to mitigate this problem.
> +             */
> +            warn_report_once(
> +                "Using vfio with vIOMMUs and coordinated discarding of"
> +                " RAM (e.g., virtio-mem) works, however, malicious"
> +                " guests can trigger pinning of more memory than"
> +                " intended via an IOMMU. It's possible to mitigate "
> +                " by setting/adjusting RLIMIT_MEMLOCK.");
> +        }
>          /*
>           * vaddr is only valid until rcu_read_unlock(). But after
>           * vfio_dma_map has set up the mapping the pages will be
> @@ -1349,6 +1285,7 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>      VFIOContainer *container = giommu->container;
>      hwaddr iova = iotlb->iova + giommu->iommu_offset;
>      ram_addr_t translated_addr;
> +    bool mr_has_discard_manager;
>  
>      trace_vfio_iommu_map_dirty_notify(iova, iova + iotlb->addr_mask);
>  
> @@ -1359,9 +1296,9 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>      }
>  
>      rcu_read_lock();
> -    if (vfio_get_xlat_addr(iotlb, NULL, &translated_addr, NULL)) {
> +    if (memory_get_xlat_addr(iotlb, NULL, &translated_addr, NULL,
> +                             &mr_has_discard_manager)) {
>          int ret;
> -
>          ret = vfio_get_dirty_bitmap(container, iova, iotlb->addr_mask + 1,
>                                      translated_addr);
>          if (ret) {
> @@ -1370,6 +1307,26 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
>                           container, iova,
>                           iotlb->addr_mask + 1, ret);
>          }
> +        if (mr_has_discard_manager) {
> +            /*
> +             * Malicious VMs might trigger discarding of IOMMU-mapped memory.
> +             * The pages will remain pinned inside vfio until unmapped,
> +             * resulting in a higher memory consumption than expected. If memory
> +             * would get populated again later, there would be an inconsistency
> +             * between pages pinned by vfio and pages seen by QEMU. This is the
> +             * case until unmapped from the IOMMU (e.g., during device reset).
> +             *
> +             * With malicious guests, we really only care about pinning more
> +             * memory than expected. RLIMIT_MEMLOCK set for the user/process can
> +             * never be exceeded and can be used to mitigate this problem.
> +             */
> +            warn_report_once(
> +                "Using vfio with vIOMMUs and coordinated discarding of"
> +                " RAM (e.g., virtio-mem) works, however, malicious"
> +                " guests can trigger pinning of more memory than"
> +                " intended via an IOMMU. It's possible to mitigate "
> +                " by setting/adjusting RLIMIT_MEMLOCK.");
> +        }

This still needs a vfio wrapper to avoid the duplicate comment and
warn_report_once.  Thanks,

Alex


>      }
>      rcu_read_unlock();
>  }
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index bfb1de8eea..d1e79c39dc 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -713,6 +713,10 @@ void ram_discard_manager_register_listener(RamDiscardManager *rdm,
>  void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
>                                               RamDiscardListener *rdl);
>  
> +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> +                          ram_addr_t *ram_addr, bool *read_only,
> +                          bool *mr_has_discard_manager);
> +
>  typedef struct CoalescedMemoryRange CoalescedMemoryRange;
>  typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd;
>  
> diff --git a/softmmu/memory.c b/softmmu/memory.c
> index 7ba2048836..bc0be3f62c 100644
> --- a/softmmu/memory.c
> +++ b/softmmu/memory.c
> @@ -33,6 +33,7 @@
>  #include "qemu/accel.h"
>  #include "hw/boards.h"
>  #include "migration/vmstate.h"
> +#include "exec/address-spaces.h"
>  
>  //#define DEBUG_UNASSIGNED
>  
> @@ -2121,6 +2122,77 @@ void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
>      rdmc->unregister_listener(rdm, rdl);
>  }
>  
> +/* Called with rcu_read_lock held.  */
> +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> +                          ram_addr_t *ram_addr, bool *read_only,
> +                          bool *mr_has_discard_manager)
> +{
> +    MemoryRegion *mr;
> +    hwaddr xlat;
> +    hwaddr len = iotlb->addr_mask + 1;
> +    bool writable = iotlb->perm & IOMMU_WO;
> +
> +    if (mr_has_discard_manager) {
> +        *mr_has_discard_manager = false;
> +    }
> +    /*
> +     * The IOMMU TLB entry we have just covers translation through
> +     * this IOMMU to its immediate target.  We need to translate
> +     * it the rest of the way through to memory.
> +     */
> +    mr = address_space_translate(&address_space_memory, iotlb->translated_addr,
> +                                 &xlat, &len, writable, MEMTXATTRS_UNSPECIFIED);
> +    if (!memory_region_is_ram(mr)) {
> +        error_report("iommu map to non memory area %" HWADDR_PRIx "", xlat);
> +        return false;
> +    } else if (memory_region_has_ram_discard_manager(mr)) {
> +        RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr);
> +        MemoryRegionSection tmp = {
> +            .mr = mr,
> +            .offset_within_region = xlat,
> +            .size = int128_make64(len),
> +        };
> +        if (mr_has_discard_manager) {
> +            *mr_has_discard_manager = true;
> +        }
> +        /*
> +         * Malicious VMs can map memory into the IOMMU, which is expected
> +         * to remain discarded. vfio will pin all pages, populating memory.
> +         * Disallow that. vmstate priorities make sure any RamDiscardManager
> +         * were already restored before IOMMUs are restored.
> +         */
> +        if (!ram_discard_manager_is_populated(rdm, &tmp)) {
> +            error_report("iommu map to discarded memory (e.g., unplugged via"
> +                         " virtio-mem): %" HWADDR_PRIx "",
> +                         iotlb->translated_addr);
> +            return false;
> +        }
> +    }
> +
> +    /*
> +     * Translation truncates length to the IOMMU page size,
> +     * check that it did not truncate too much.
> +     */
> +    if (len & iotlb->addr_mask) {
> +        error_report("iommu has granularity incompatible with target AS");
> +        return false;
> +    }
> +
> +    if (vaddr) {
> +        *vaddr = memory_region_get_ram_ptr(mr) + xlat;
> +    }
> +
> +    if (ram_addr) {
> +        *ram_addr = memory_region_get_ram_addr(mr) + xlat;
> +    }
> +
> +    if (read_only) {
> +        *read_only = !writable || mr->readonly;
> +    }
> +
> +    return true;
> +}
> +
>  void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
>  {
>      uint8_t mask = 1 << client;

Re: [PATCH v6 1/2] vfio: move function vfio_get_xlat_addr() to memory.c

[Cindy Lu]

On Sun, 30 Oct 2022 at 21:02, Alex Williamson
<alex.williamson@redhat.com> wrote:
>
> On Sun, 30 Oct 2022 14:01:05 +0800
> Cindy Lu <lulu@redhat.com> wrote:
>
> > - Move the function vfio_get_xlat_addr to softmmu/memory.c, and
> >   change the name to memory_get_xlat_addr(). So we can use this
> >   function on other devices, such as vDPA device.
> > - Add a new bool arg in this function, which shows whether the memory is
> >   backed by a discard manager. So the device can have its own warning.
> >
> > Signed-off-by: Cindy Lu <lulu@redhat.com>
> > ---
> >  hw/vfio/common.c      | 135 ++++++++++++++----------------------------
> >  include/exec/memory.h |   4 ++
> >  softmmu/memory.c      |  72 ++++++++++++++++++++++
> >  3 files changed, 122 insertions(+), 89 deletions(-)
> >
> > diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> > index ace9562a9b..06ebbb82c7 100644
> > --- a/hw/vfio/common.c
> > +++ b/hw/vfio/common.c
> > @@ -574,92 +574,6 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section)
> >             section->offset_within_address_space & (1ULL << 63);
> >  }
> >
> > -/* Called with rcu_read_lock held.  */
> > -static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> > -                               ram_addr_t *ram_addr, bool *read_only)
> > -{
> > -    MemoryRegion *mr;
> > -    hwaddr xlat;
> > -    hwaddr len = iotlb->addr_mask + 1;
> > -    bool writable = iotlb->perm & IOMMU_WO;
> > -
> > -    /*
> > -     * The IOMMU TLB entry we have just covers translation through
> > -     * this IOMMU to its immediate target.  We need to translate
> > -     * it the rest of the way through to memory.
> > -     */
> > -    mr = address_space_translate(&address_space_memory,
> > -                                 iotlb->translated_addr,
> > -                                 &xlat, &len, writable,
> > -                                 MEMTXATTRS_UNSPECIFIED);
> > -    if (!memory_region_is_ram(mr)) {
> > -        error_report("iommu map to non memory area %"HWADDR_PRIx"",
> > -                     xlat);
> > -        return false;
> > -    } else if (memory_region_has_ram_discard_manager(mr)) {
> > -        RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr);
> > -        MemoryRegionSection tmp = {
> > -            .mr = mr,
> > -            .offset_within_region = xlat,
> > -            .size = int128_make64(len),
> > -        };
> > -
> > -        /*
> > -         * Malicious VMs can map memory into the IOMMU, which is expected
> > -         * to remain discarded. vfio will pin all pages, populating memory.
> > -         * Disallow that. vmstate priorities make sure any RamDiscardManager
> > -         * were already restored before IOMMUs are restored.
> > -         */
> > -        if (!ram_discard_manager_is_populated(rdm, &tmp)) {
> > -            error_report("iommu map to discarded memory (e.g., unplugged via"
> > -                         " virtio-mem): %"HWADDR_PRIx"",
> > -                         iotlb->translated_addr);
> > -            return false;
> > -        }
> > -
> > -        /*
> > -         * Malicious VMs might trigger discarding of IOMMU-mapped memory. The
> > -         * pages will remain pinned inside vfio until unmapped, resulting in a
> > -         * higher memory consumption than expected. If memory would get
> > -         * populated again later, there would be an inconsistency between pages
> > -         * pinned by vfio and pages seen by QEMU. This is the case until
> > -         * unmapped from the IOMMU (e.g., during device reset).
> > -         *
> > -         * With malicious guests, we really only care about pinning more memory
> > -         * than expected. RLIMIT_MEMLOCK set for the user/process can never be
> > -         * exceeded and can be used to mitigate this problem.
> > -         */
> > -        warn_report_once("Using vfio with vIOMMUs and coordinated discarding of"
> > -                         " RAM (e.g., virtio-mem) works, however, malicious"
> > -                         " guests can trigger pinning of more memory than"
> > -                         " intended via an IOMMU. It's possible to mitigate "
> > -                         " by setting/adjusting RLIMIT_MEMLOCK.");
> > -    }
> > -
> > -    /*
> > -     * Translation truncates length to the IOMMU page size,
> > -     * check that it did not truncate too much.
> > -     */
> > -    if (len & iotlb->addr_mask) {
> > -        error_report("iommu has granularity incompatible with target AS");
> > -        return false;
> > -    }
> > -
> > -    if (vaddr) {
> > -        *vaddr = memory_region_get_ram_ptr(mr) + xlat;
> > -    }
> > -
> > -    if (ram_addr) {
> > -        *ram_addr = memory_region_get_ram_addr(mr) + xlat;
> > -    }
> > -
> > -    if (read_only) {
> > -        *read_only = !writable || mr->readonly;
> > -    }
> > -
> > -    return true;
> > -}
> > -
> >  static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> >  {
> >      VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n);
> > @@ -681,10 +595,32 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> >
> >      if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) {
> >          bool read_only;
> > +        bool mr_has_discard_manager;
> >
> > -        if (!vfio_get_xlat_addr(iotlb, &vaddr, NULL, &read_only)) {
> > +        if (!memory_get_xlat_addr(iotlb, &vaddr, NULL, &read_only,
> > +                                  &mr_has_discard_manager)) {
> >              goto out;
> >          }
> > +        if (mr_has_discard_manager) {
> > +            /*
> > +             * Malicious VMs might trigger discarding of IOMMU-mapped memory.
> > +             * The pages will remain pinned inside vfio until unmapped,
> > +             * resulting in a higher memory consumption than expected. If memory
> > +             * would get populated again later, there would be an inconsistency
> > +             * between pages pinned by vfio and pages seen by QEMU. This is the
> > +             * case until unmapped from the IOMMU (e.g., during device reset).
> > +             *
> > +             * With malicious guests, we really only care about pinning more
> > +             * memory than expected. RLIMIT_MEMLOCK set for the user/process can
> > +             * never be exceeded and can be used to mitigate this problem.
> > +             */
> > +            warn_report_once(
> > +                "Using vfio with vIOMMUs and coordinated discarding of"
> > +                " RAM (e.g., virtio-mem) works, however, malicious"
> > +                " guests can trigger pinning of more memory than"
> > +                " intended via an IOMMU. It's possible to mitigate "
> > +                " by setting/adjusting RLIMIT_MEMLOCK.");
> > +        }
> >          /*
> >           * vaddr is only valid until rcu_read_unlock(). But after
> >           * vfio_dma_map has set up the mapping the pages will be
> > @@ -1349,6 +1285,7 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> >      VFIOContainer *container = giommu->container;
> >      hwaddr iova = iotlb->iova + giommu->iommu_offset;
> >      ram_addr_t translated_addr;
> > +    bool mr_has_discard_manager;
> >
> >      trace_vfio_iommu_map_dirty_notify(iova, iova + iotlb->addr_mask);
> >
> > @@ -1359,9 +1296,9 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> >      }
> >
> >      rcu_read_lock();
> > -    if (vfio_get_xlat_addr(iotlb, NULL, &translated_addr, NULL)) {
> > +    if (memory_get_xlat_addr(iotlb, NULL, &translated_addr, NULL,
> > +                             &mr_has_discard_manager)) {
> >          int ret;
> > -
> >          ret = vfio_get_dirty_bitmap(container, iova, iotlb->addr_mask + 1,
> >                                      translated_addr);
> >          if (ret) {
> > @@ -1370,6 +1307,26 @@ static void vfio_iommu_map_dirty_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> >                           container, iova,
> >                           iotlb->addr_mask + 1, ret);
> >          }
> > +        if (mr_has_discard_manager) {
> > +            /*
> > +             * Malicious VMs might trigger discarding of IOMMU-mapped memory.
> > +             * The pages will remain pinned inside vfio until unmapped,
> > +             * resulting in a higher memory consumption than expected. If memory
> > +             * would get populated again later, there would be an inconsistency
> > +             * between pages pinned by vfio and pages seen by QEMU. This is the
> > +             * case until unmapped from the IOMMU (e.g., during device reset).
> > +             *
> > +             * With malicious guests, we really only care about pinning more
> > +             * memory than expected. RLIMIT_MEMLOCK set for the user/process can
> > +             * never be exceeded and can be used to mitigate this problem.
> > +             */
> > +            warn_report_once(
> > +                "Using vfio with vIOMMUs and coordinated discarding of"
> > +                " RAM (e.g., virtio-mem) works, however, malicious"
> > +                " guests can trigger pinning of more memory than"
> > +                " intended via an IOMMU. It's possible to mitigate "
> > +                " by setting/adjusting RLIMIT_MEMLOCK.");
> > +        }
>
> This still needs a vfio wrapper to avoid the duplicate comment and
> warn_report_once.  Thanks,
>
> Alex
>
sure, will change this ,Thanks Alex
Thanks
Cindy
>
> >      }
> >      rcu_read_unlock();
> >  }
> > diff --git a/include/exec/memory.h b/include/exec/memory.h
> > index bfb1de8eea..d1e79c39dc 100644
> > --- a/include/exec/memory.h
> > +++ b/include/exec/memory.h
> > @@ -713,6 +713,10 @@ void ram_discard_manager_register_listener(RamDiscardManager *rdm,
> >  void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
> >                                               RamDiscardListener *rdl);
> >
> > +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> > +                          ram_addr_t *ram_addr, bool *read_only,
> > +                          bool *mr_has_discard_manager);
> > +
> >  typedef struct CoalescedMemoryRange CoalescedMemoryRange;
> >  typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd;
> >
> > diff --git a/softmmu/memory.c b/softmmu/memory.c
> > index 7ba2048836..bc0be3f62c 100644
> > --- a/softmmu/memory.c
> > +++ b/softmmu/memory.c
> > @@ -33,6 +33,7 @@
> >  #include "qemu/accel.h"
> >  #include "hw/boards.h"
> >  #include "migration/vmstate.h"
> > +#include "exec/address-spaces.h"
> >
> >  //#define DEBUG_UNASSIGNED
> >
> > @@ -2121,6 +2122,77 @@ void ram_discard_manager_unregister_listener(RamDiscardManager *rdm,
> >      rdmc->unregister_listener(rdm, rdl);
> >  }
> >
> > +/* Called with rcu_read_lock held.  */
> > +bool memory_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
> > +                          ram_addr_t *ram_addr, bool *read_only,
> > +                          bool *mr_has_discard_manager)
> > +{
> > +    MemoryRegion *mr;
> > +    hwaddr xlat;
> > +    hwaddr len = iotlb->addr_mask + 1;
> > +    bool writable = iotlb->perm & IOMMU_WO;
> > +
> > +    if (mr_has_discard_manager) {
> > +        *mr_has_discard_manager = false;
> > +    }
> > +    /*
> > +     * The IOMMU TLB entry we have just covers translation through
> > +     * this IOMMU to its immediate target.  We need to translate
> > +     * it the rest of the way through to memory.
> > +     */
> > +    mr = address_space_translate(&address_space_memory, iotlb->translated_addr,
> > +                                 &xlat, &len, writable, MEMTXATTRS_UNSPECIFIED);
> > +    if (!memory_region_is_ram(mr)) {
> > +        error_report("iommu map to non memory area %" HWADDR_PRIx "", xlat);
> > +        return false;
> > +    } else if (memory_region_has_ram_discard_manager(mr)) {
> > +        RamDiscardManager *rdm = memory_region_get_ram_discard_manager(mr);
> > +        MemoryRegionSection tmp = {
> > +            .mr = mr,
> > +            .offset_within_region = xlat,
> > +            .size = int128_make64(len),
> > +        };
> > +        if (mr_has_discard_manager) {
> > +            *mr_has_discard_manager = true;
> > +        }
> > +        /*
> > +         * Malicious VMs can map memory into the IOMMU, which is expected
> > +         * to remain discarded. vfio will pin all pages, populating memory.
> > +         * Disallow that. vmstate priorities make sure any RamDiscardManager
> > +         * were already restored before IOMMUs are restored.
> > +         */
> > +        if (!ram_discard_manager_is_populated(rdm, &tmp)) {
> > +            error_report("iommu map to discarded memory (e.g., unplugged via"
> > +                         " virtio-mem): %" HWADDR_PRIx "",
> > +                         iotlb->translated_addr);
> > +            return false;
> > +        }
> > +    }
> > +
> > +    /*
> > +     * Translation truncates length to the IOMMU page size,
> > +     * check that it did not truncate too much.
> > +     */
> > +    if (len & iotlb->addr_mask) {
> > +        error_report("iommu has granularity incompatible with target AS");
> > +        return false;
> > +    }
> > +
> > +    if (vaddr) {
> > +        *vaddr = memory_region_get_ram_ptr(mr) + xlat;
> > +    }
> > +
> > +    if (ram_addr) {
> > +        *ram_addr = memory_region_get_ram_addr(mr) + xlat;
> > +    }
> > +
> > +    if (read_only) {
> > +        *read_only = !writable || mr->readonly;
> > +    }
> > +
> > +    return true;
> > +}
> > +
> >  void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
> >  {
> >      uint8_t mask = 1 << client;
>