Re: [PATCH V3 31/42] vfio/iommufd: use IOMMU_IOAS_MAP_FILE

[Steven Sistare]

On 5/19/2025 11:52 AM, Steven Sistare wrote:

On 5/16/2025 4:48 AM, Duan, Zhenzhong wrote:

-----Original Message-----
From: Steve Sistare <steven.sist...@oracle.com>
Subject: [PATCH V3 31/42] vfio/iommufd: use IOMMU_IOAS_MAP_FILE

Use IOMMU_IOAS_MAP_FILE when the mapped region is backed by a file.
Such a mapping can be preserved without modification during CPR,
because it depends on the file's address space, which does not change,
rather than on the process's address space, which does change.

Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
---
hw/vfio/container-base.c              |  9 +++++++++
hw/vfio/iommufd.c                     | 13 +++++++++++++
include/hw/vfio/vfio-container-base.h |  3 +++
3 files changed, 25 insertions(+)

diff --git a/hw/vfio/container-base.c b/hw/vfio/container-base.c
index 8f43bc8..72a51a6 100644
--- a/hw/vfio/container-base.c
+++ b/hw/vfio/container-base.c
@@ -79,7 +79,16 @@ int vfio_container_dma_map(VFIOContainerBase
*bcontainer,
                            RAMBlock *rb)
{
     VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
+    int mfd = rb ? qemu_ram_get_fd(rb) : -1;

+    if (mfd >= 0 && vioc->dma_map_file) {
+        unsigned long start = vaddr - qemu_ram_get_host_addr(rb);
+        unsigned long offset = qemu_ram_get_fd_offset(rb);
+
+        vioc->dma_map_file(bcontainer, iova, size, mfd, start + offset,
+                           readonly);

Shouldn't we return result to call site?

Yes!  Good catch, thanks.

With that simple fix:
  return vioc->dma_map_file(...)
can I add your RB?

- Steve

+        return 0;
+    }
     g_assert(vioc->dma_map);
     return vioc->dma_map(bcontainer, iova, size, vaddr, readonly);
}
diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
index 167bda4..6eb417a 100644
--- a/hw/vfio/iommufd.c
+++ b/hw/vfio/iommufd.c
@@ -44,6 +44,18 @@ static int iommufd_cdev_map(const VFIOContainerBase
*bcontainer, hwaddr iova,
                                    iova, size, vaddr, readonly);
}

+static int iommufd_cdev_map_file(const VFIOContainerBase *bcontainer,
+                                 hwaddr iova, ram_addr_t size,
+                                 int fd, unsigned long start, bool readonly)
+{
+    const VFIOIOMMUFDContainer *container =
+        container_of(bcontainer, VFIOIOMMUFDContainer, bcontainer);
+
+    return iommufd_backend_map_file_dma(container->be,
+                                        container->ioas_id,
+                                        iova, size, fd, start, readonly);
+}
+
static int iommufd_cdev_unmap(const VFIOContainerBase *bcontainer,
                               hwaddr iova, ram_addr_t size,
                               IOMMUTLBEntry *iotlb, bool unmap_all)
@@ -802,6 +814,7 @@ static void vfio_iommu_iommufd_class_init(ObjectClass
*klass, const void *data)
     VFIOIOMMUClass *vioc = VFIO_IOMMU_CLASS(klass);

     vioc->dma_map = iommufd_cdev_map;
+    vioc->dma_map_file = iommufd_cdev_map_file;
     vioc->dma_unmap = iommufd_cdev_unmap;
     vioc->attach_device = iommufd_cdev_attach;
     vioc->detach_device = iommufd_cdev_detach;
diff --git a/include/hw/vfio/vfio-container-base.h b/include/hw/vfio/vfio-
container-base.h
index 03b3f9c..f30f828 100644
--- a/include/hw/vfio/vfio-container-base.h
+++ b/include/hw/vfio/vfio-container-base.h
@@ -123,6 +123,9 @@ struct VFIOIOMMUClass {
     int (*dma_map)(const VFIOContainerBase *bcontainer,
                    hwaddr iova, ram_addr_t size,
                    void *vaddr, bool readonly);
+    int (*dma_map_file)(const VFIOContainerBase *bcontainer,
+                        hwaddr iova, ram_addr_t size,
+                        int fd, unsigned long start, bool readonly);
     /**
      * @dma_unmap
      *
--
1.8.3.1