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Re: [PATCH v16 QEMU 14/16] vfio: Add vfio_listener_log_sync to mark dirt

From: Kirti Wankhede
Subject: Re: [PATCH v16 QEMU 14/16] vfio: Add vfio_listener_log_sync to mark dirty pages
Date: Sat, 4 Apr 2020 01:41:45 +0530
User-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 


On 4/1/2020 11:20 AM, Yan Zhao wrote:

On Wed, Mar 25, 2020 at 05:09:12AM +0800, Kirti Wankhede wrote:

vfio_listener_log_sync gets list of dirty pages from container using
VFIO_IOMMU_GET_DIRTY_BITMAP ioctl and mark those pages dirty when all
devices are stopped and saving state.
Return early for the RAM block section of mapped MMIO region.

Signed-off-by: Kirti Wankhede <address@hidden>
Reviewed-by: Neo Jia <address@hidden>
---
  hw/vfio/common.c     | 200 +++++++++++++++++++++++++++++++++++++++++++++++++--
  hw/vfio/trace-events |   1 +
  2 files changed, 196 insertions(+), 5 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 4a2f0d6a2233..6d41e1ac5c2f 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -29,6 +29,7 @@
  #include "hw/vfio/vfio.h"
  #include "exec/address-spaces.h"
  #include "exec/memory.h"
+#include "exec/ram_addr.h"
  #include "hw/hw.h"
  #include "qemu/error-report.h"
  #include "qemu/main-loop.h"
@@ -38,6 +39,7 @@
  #include "sysemu/reset.h"
  #include "trace.h"
  #include "qapi/error.h"
+#include "migration/migration.h"
VFIOGroupList vfio_group_list = 
      QLIST_HEAD_INITIALIZER(vfio_group_list);
@@ -288,6 +290,28 @@ const MemoryRegionOps vfio_region_ops = {
  };
/* 
+ * Device state interfaces
+ */
+
+static bool vfio_devices_are_stopped_and_saving(void)
+{
+    VFIOGroup *group;
+    VFIODevice *vbasedev;
+
+    QLIST_FOREACH(group, &vfio_group_list, next) {
+        QLIST_FOREACH(vbasedev, &group->device_list, next) {
+            if ((vbasedev->device_state & VFIO_DEVICE_STATE_SAVING) &&
+                !(vbasedev->device_state & VFIO_DEVICE_STATE_RUNNING)) {
+                continue;
+            } else {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+/*
   * DMA - Mapping and unmapping for the "type1" IOMMU interface used on x86
   */
  static int vfio_dma_unmap(VFIOContainer *container,
@@ -408,8 +432,8 @@ static bool 
vfio_listener_skipped_section(MemoryRegionSection *section)
  }
/* Called with rcu_read_lock held. */ 
-static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void **vaddr,
-                           bool *read_only)
+static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr,
+                               ram_addr_t *ram_addr, bool *read_only)
  {
      MemoryRegion *mr;
      hwaddr xlat;
@@ -440,9 +464,17 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void 
**vaddr,
          return false;
      }
- *vaddr = memory_region_get_ram_ptr(mr) + xlat; 
-    *read_only = !writable || mr->readonly;
+    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;
  }
@@ -467,7 +499,7 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb) 
      rcu_read_lock();
if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) { 
-        if (!vfio_get_vaddr(iotlb, &vaddr, &read_only)) {
+        if (!vfio_get_xlat_addr(iotlb, &vaddr, NULL, &read_only)) {
              goto out;
          }
          /*
@@ -813,9 +845,167 @@ static void vfio_listener_region_del(MemoryListener 
*listener,
      }
  }
+static int vfio_get_dirty_bitmap(MemoryListener *listener, 
+                                 MemoryRegionSection *section)
+{
+    VFIOContainer *container = container_of(listener, VFIOContainer, listener);
+    VFIOGuestIOMMU *giommu;
+    IOMMUTLBEntry iotlb;
+    hwaddr granularity, address_limit, iova;
+    int ret;
+
+    if (memory_region_is_iommu(section->mr)) {
+        QLIST_FOREACH(giommu, &container->giommu_list, giommu_next) {
+            if (MEMORY_REGION(giommu->iommu) == section->mr &&
+                giommu->n.start == section->offset_within_region) {
+                break;
+            }
+        }
+
+        if (!giommu) {
+            return -EINVAL;
+        }
+    }
+
+    if (memory_region_is_iommu(section->mr)) {
+        granularity = memory_region_iommu_get_min_page_size(giommu->iommu);
+
+        address_limit = MIN(int128_get64(section->size),
+                            
memory_region_iommu_get_address_limit(giommu->iommu,
+                                                 int128_get64(section->size)));
+    } else {
+        granularity = memory_region_size(section->mr);
+        address_limit = int128_get64(section->size);
+    }
+
+    iova = TARGET_PAGE_ALIGN(section->offset_within_address_space);
+
+    RCU_READ_LOCK_GUARD();
+


the requirement of iova < address_limit is not right. reason as blow:
when vIOMMU is NOT on,
iova is section->offset_within_address_space,
address_limit is section->size,
but iova has not reason to be less than address_limit.

for example, when vm memory size is large than 3G (e.g.4G)
for memory region section of range (0x100000000-0x13fffffff),
its iova is 0x100000000, address_limit is 0x40000000,
then as iova is not less than address_limit, dirty pages query for memory
3G-4G will be skipped.
Therefore dirty pages in 3G-4G will be lost.




Right, thanks. Fixing it. address_limit should be iova + size - 1
I did basic API testing with 2G memory. I'll make sure to test with more than 4G to catch such bugs. 

Thanks,
Kirti



+    while (iova < address_limit) {
+        struct vfio_iommu_type1_dirty_bitmap *dbitmap;
+        struct vfio_iommu_type1_dirty_bitmap_get *range;
+        ram_addr_t start, pages;
+        uint64_t iova_xlat, size;
+
+        if (memory_region_is_iommu(section->mr)) {
+            iotlb = address_space_get_iotlb_entry(container->space->as, iova,
+                                                 true, MEMTXATTRS_UNSPECIFIED);
+            if ((iotlb.target_as == NULL) || (iotlb.addr_mask == 0)) {
+                if ((iova + granularity) < iova) {
+                    break;
+                }
+                iova += granularity;
+                continue;
+            }
+            iova_xlat = iotlb.iova + giommu->iommu_offset;
+            size = iotlb.addr_mask + 1;
+        } else {
+            iova_xlat = iova;
+            size = address_limit;
+        }
+
+        dbitmap = g_malloc0(sizeof(*dbitmap) + sizeof(*range));
+        if (!dbitmap) {
+            return -ENOMEM;
+        }
+
+        dbitmap->argsz = sizeof(*dbitmap) + sizeof(*range);
+        dbitmap->flags = VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP;
+        range = (struct vfio_iommu_type1_dirty_bitmap_get *)&dbitmap->data;
+        range->iova = iova_xlat;
+        range->size = size;
+
+        /*
+         * cpu_physical_memory_set_dirty_lebitmap() expects pages in bitmap of
+         * TARGET_PAGE_SIZE to mark those dirty. Hence set bitmap's pgsize to
+         * TARGET_PAGE_SIZE.
+         */
+        range->bitmap.pgsize = TARGET_PAGE_SIZE;
+
+        /*
+         * Comment from kvm_physical_sync_dirty_bitmap() since same applies 
here
+         * XXX bad kernel interface alert
+         * For dirty bitmap, kernel allocates array of size aligned to
+         * bits-per-long.  But for case when the kernel is 64bits and
+         * the userspace is 32bits, userspace can't align to the same
+         * bits-per-long, since sizeof(long) is different between kernel
+         * and user space.  This way, userspace will provide buffer which
+         * may be 4 bytes less than the kernel will use, resulting in
+         * userspace memory corruption (which is not detectable by valgrind
+         * too, in most cases).
+         * So for now, let's align to 64 instead of HOST_LONG_BITS here, in
+         * a hope that sizeof(long) won't become >8 any time soon.
+         */
+
+        pages = TARGET_PAGE_ALIGN(range->size) >> TARGET_PAGE_BITS;
+        range->bitmap.size = ROUND_UP(pages, 64) / 8;
+        range->bitmap.data = g_malloc0(range->bitmap.size);
+        if (range->bitmap.data == NULL) {
+            error_report("Error allocating bitmap of size 0x%llx",
+                         range->bitmap.size);
+            ret = -ENOMEM;
+            goto err_out;
+        }
+
+        ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, dbitmap);
+        if (ret) {
+            error_report("Failed to get dirty bitmap for iova: 0x%llx "
+                         "size: 0x%llx err: %d",
+                         range->iova, range->size, errno);
+            goto err_out;
+        }
+
+        if (memory_region_is_iommu(section->mr)) {
+            if (!vfio_get_xlat_addr(&iotlb, NULL, &start, NULL)) {
+                ret = -EINVAL;
+                goto err_out;
+            }
+        } else {
+            start = memory_region_get_ram_addr(section->mr) +
+                    section->offset_within_region + iova -
+                    TARGET_PAGE_ALIGN(section->offset_within_address_space);
+        }
+
+        cpu_physical_memory_set_dirty_lebitmap((uint64_t *)range->bitmap.data,
+                                               start, pages);
+
+        trace_vfio_get_dirty_bitmap(container->fd, range->iova, range->size,
+                                    range->bitmap.size, start);
+err_out:
+        g_free(range->bitmap.data);
+        g_free(dbitmap);
+
+        if (ret) {
+            return ret;
+        }
+
+        if ((iova + size) < iova) {
+            break;
+        }
+
+        iova += size;
+    }
+
+    return 0;
+}
+
+static void vfio_listerner_log_sync(MemoryListener *listener,
+        MemoryRegionSection *section)
+{
+    if (vfio_listener_skipped_section(section)) {
+        return;
+    }
+
+    if (vfio_devices_are_stopped_and_saving()) {
+        vfio_get_dirty_bitmap(listener, section);
+    }
+}
+
  static const MemoryListener vfio_memory_listener = {
      .region_add = vfio_listener_region_add,
      .region_del = vfio_listener_region_del,
+    .log_sync = vfio_listerner_log_sync,
  };
static void vfio_listener_release(VFIOContainer *container) 
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index ac065b559f4e..bc8f35ee9356 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -160,3 +160,4 @@ vfio_save_complete_precopy(char *name) " (%s)"
  vfio_load_device_config_state(char *name) " (%s)"
  vfio_load_state(char *name, uint64_t data) " (%s) data 0x%"PRIx64
  vfio_load_state_device_data(char *name, uint64_t data_offset, uint64_t data_size) " (%s) 
Offset 0x%"PRIx64" size 0x%"PRIx64
+vfio_get_dirty_bitmap(int fd, uint64_t iova, uint64_t size, uint64_t bitmap_size, uint64_t start) "container 
fd=%d, iova=0x%"PRIx64" size= 0x%"PRIx64" bitmap_size=0x%"PRIx64" start=0x%"PRIx64
--
2.7.0
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