Re: [PATCH v6 1/9] vfio: Add Error** argument to .set_dirty_page_tracking() handler

[Cédric Le Goater]

On 5/15/24 08:40, Eric Auger wrote:

Hi Cédric,

On 5/14/24 17:31, Cédric Le Goater wrote:

We will use the Error object to improve error reporting in the
.log_global*() handlers of VFIO. Add documentation while at it.

Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org>
Reviewed-by: Avihai Horon <avih...@nvidia.com>
Signed-off-by: Cédric Le Goater <c...@redhat.com>
---
  Changes in v5:

  - Fixed typo in set_dirty_page_tracking documentation

include/hw/vfio/vfio-container-base.h | 18 ++++++++++++++++--

  hw/vfio/common.c                      |  4 ++--
  hw/vfio/container-base.c              |  4 ++--
  hw/vfio/container.c                   |  6 +++---
  4 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/include/hw/vfio/vfio-container-base.h 
b/include/hw/vfio/vfio-container-base.h
index 
3582d5f97a37877b2adfc0d0b06996c82403f8b7..326ceea52a2030eec9dad289a9845866c4a8c090
 100644
--- a/include/hw/vfio/vfio-container-base.h
+++ b/include/hw/vfio/vfio-container-base.h
@@ -82,7 +82,7 @@ int vfio_container_add_section_window(VFIOContainerBase 
*bcontainer,
  void vfio_container_del_section_window(VFIOContainerBase *bcontainer,
                                         MemoryRegionSection *section);
  int vfio_container_set_dirty_page_tracking(VFIOContainerBase *bcontainer,
-                                           bool start);
+                                           bool start, Error **errp);

I am a bit confused now wrt [PATCH v2 03/11] vfio: Make
VFIOIOMMUClass::attach_device() and its wrapper return bool & co

Shall we return a bool or a int?

It would be better to follow the best practices described in qapi/error.h.

Zhenzhong excluded some files from his cleanup series to avoid conflicts
with this series of mine. And indeed, I would prefer to merge this one
first. It should be addressed later.

Looking at ./include/qapi/error.h I have not found any stringent requirement

  * - Whenever practical, also return a value that indicates success /
  *   failure.  This can make the error checking more concise, and can
  *   avoid useless error object creation and destruction.  Note that
  *   we still have many functions returning void.  We recommend
  *   • bool-valued functions return true on success / false on failure,
  *   • pointer-valued functions return non-null / null pointer, and
  *   • integer-valued functions return non-negative / negative.

  int vfio_container_query_dirty_bitmap(const VFIOContainerBase *bcontainer,
                                        VFIOBitmap *vbmap,
                                        hwaddr iova, hwaddr size);
@@ -121,9 +121,23 @@ struct VFIOIOMMUClass {
      int (*attach_device)(const char *name, VFIODevice *vbasedev,
                           AddressSpace *as, Error **errp);
      void (*detach_device)(VFIODevice *vbasedev);
+
      /* migration feature */
+
+    /**
+     * @set_dirty_page_tracking
+     *
+     * Start or stop dirty pages tracking on VFIO container
+     *
+     * @bcontainer: #VFIOContainerBase on which to de/activate dirty
+     *              page tracking
+     * @start: indicates whether to start or stop dirty pages tracking
+     * @errp: pointer to Error*, to store an error if it happens.
+     *
+     * Returns zero to indicate success and negative for error
+     */
      int (*set_dirty_page_tracking)(const VFIOContainerBase *bcontainer,
-                                   bool start);
+                                   bool start, Error **errp);
      int (*query_dirty_bitmap)(const VFIOContainerBase *bcontainer,
                                VFIOBitmap *vbmap,
                                hwaddr iova, hwaddr size);
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 
8f9cbdc0264044ce587877a7d19d14b28527291b..485e53916491f1164d29e739fb7106c0c77df737
 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -1076,7 +1076,7 @@ static bool vfio_listener_log_global_start(MemoryListener 
*listener,
      if (vfio_devices_all_device_dirty_tracking(bcontainer)) {
          ret = vfio_devices_dma_logging_start(bcontainer);
      } else {
-        ret = vfio_container_set_dirty_page_tracking(bcontainer, true);
+        ret = vfio_container_set_dirty_page_tracking(bcontainer, true, NULL);
      }

if (ret) {

@@ -1096,7 +1096,7 @@ static void vfio_listener_log_global_stop(MemoryListener 
*listener)
      if (vfio_devices_all_device_dirty_tracking(bcontainer)) {
          vfio_devices_dma_logging_stop(bcontainer);
      } else {
-        ret = vfio_container_set_dirty_page_tracking(bcontainer, false);
+        ret = vfio_container_set_dirty_page_tracking(bcontainer, false, NULL);
      }

if (ret) {

diff --git a/hw/vfio/container-base.c b/hw/vfio/container-base.c
index 
913ae49077c4f09b7b27517c1231cfbe4befb7fb..7c0764121d24b02b6c4e66e368d7dff78a6d65aa
 100644
--- a/hw/vfio/container-base.c
+++ b/hw/vfio/container-base.c
@@ -53,14 +53,14 @@ void vfio_container_del_section_window(VFIOContainerBase 
*bcontainer,
  }

int vfio_container_set_dirty_page_tracking(VFIOContainerBase *bcontainer,

-                                           bool start)
+                                           bool start, Error **errp)
  {
      if (!bcontainer->dirty_pages_supported) {
          return 0;
      }

g_assert(bcontainer->ops->set_dirty_page_tracking);

-    return bcontainer->ops->set_dirty_page_tracking(bcontainer, start);
+    return bcontainer->ops->set_dirty_page_tracking(bcontainer, start, errp);
  }

int vfio_container_query_dirty_bitmap(const VFIOContainerBase *bcontainer,

diff --git a/hw/vfio/container.c b/hw/vfio/container.c
index 
77bdec276ec49cb9cd767c0de42ec801b4421572..c35221fbe7dc5453050f97cd186fc958e24f28f7
 100644
--- a/hw/vfio/container.c
+++ b/hw/vfio/container.c
@@ -209,7 +209,7 @@ static int vfio_legacy_dma_map(const VFIOContainerBase 
*bcontainer, hwaddr iova,

static int

  vfio_legacy_set_dirty_page_tracking(const VFIOContainerBase *bcontainer,
-                                    bool start)
+                                    bool start, Error **errp)
  {
      const VFIOContainer *container = container_of(bcontainer, VFIOContainer,
                                                    bcontainer);
@@ -227,8 +227,8 @@ vfio_legacy_set_dirty_page_tracking(const VFIOContainerBase 
*bcontainer,
      ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, &dirty);
      if (ret) {
          ret = -errno;
-        error_report("Failed to set dirty tracking flag 0x%x errno: %d",
-                     dirty.flags, errno);
+        error_setg_errno(errp, errno, "Failed to set dirty tracking flag 0x%x",
+                         dirty.flags);
      }

return ret;

Besides
Reviewed-by: Eric Auger <eric.au...@redhat.com>

Eric

Thanks,

C.