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Re: [PATCH v4 01/12] vfio/pci: Extract mdev check into an helper


From: Cédric Le Goater
Subject: Re: [PATCH v4 01/12] vfio/pci: Extract mdev check into an helper
Date: Tue, 16 Jul 2024 11:21:07 +0200
User-agent: Mozilla Thunderbird

Hello Joao

On 7/12/24 13:46, Joao Martins wrote:
In preparation to skip initialization of the HostIOMMUDevice for mdev,
extract the checks that validate if a device is an mdev into helpers.

A vfio_set_mdev() is created, and subsystems consult VFIODevice::mdev
to check if it's mdev or not.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
  include/hw/vfio/vfio-common.h |  2 ++
  hw/vfio/helpers.c             | 18 ++++++++++++++++++
  hw/vfio/pci.c                 |  9 ++-------
  3 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index e8ddf92bb185..7419466bca92 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -116,6 +116,7 @@ typedef struct VFIODevice {
      DeviceState *dev;
      int fd;
      int type;
+    bool mdev;
      bool reset_works;
      bool needs_reset;
      bool no_mmap;
@@ -231,6 +232,7 @@ void vfio_region_exit(VFIORegion *region);
  void vfio_region_finalize(VFIORegion *region);
  void vfio_reset_handler(void *opaque);
  struct vfio_device_info *vfio_get_device_info(int fd);
+void vfio_set_mdev(VFIODevice *vbasedev);
  bool vfio_attach_device(char *name, VFIODevice *vbasedev,
                          AddressSpace *as, Error **errp);
  void vfio_detach_device(VFIODevice *vbasedev);
diff --git a/hw/vfio/helpers.c b/hw/vfio/helpers.c
index b14edd46edc9..bace0e788a09 100644
--- a/hw/vfio/helpers.c
+++ b/hw/vfio/helpers.c
@@ -675,3 +675,21 @@ int vfio_device_get_aw_bits(VFIODevice *vdev)
return HOST_IOMMU_DEVICE_CAP_AW_BITS_MAX;
  }
+
+void vfio_set_mdev(VFIODevice *vbasedev)

Could you please change this routine to :

  bool vfio_device_is_mdev(VFIODevice *vbasedev)

+{
+    g_autofree char *tmp = NULL;
+    char *subsys;

a g_autofree variable is preferable here.

+    bool is_mdev;
+
+    if (!vbasedev->sysfsdev) {
+        return;
+    }
+
+    tmp = g_strdup_printf("%s/subsystem", vbasedev->sysfsdev);
+    subsys = realpath(tmp, NULL);
+    is_mdev = subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);

simply return is the result here and ....

+    free(subsys);
+
+    vbasedev->mdev = is_mdev;
+}
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index e03d9f3ba546..585f23a18406 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -2963,12 +2963,10 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
      ERRP_GUARD();
      VFIOPCIDevice *vdev = VFIO_PCI(pdev);
      VFIODevice *vbasedev = &vdev->vbasedev;
-    char *subsys;
      int i, ret;
      bool is_mdev;
      char uuid[UUID_STR_LEN];
      g_autofree char *name = NULL;
-    g_autofree char *tmp = NULL;
if (vbasedev->fd < 0 && !vbasedev->sysfsdev) {
          if (!(~vdev->host.domain || ~vdev->host.bus ||
@@ -2997,11 +2995,8 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
       * stays in sync with the active working set of the guest driver.  Prevent
       * the x-balloon-allowed option unless this is minimally an mdev device.
       */
-    tmp = g_strdup_printf("%s/subsystem", vbasedev->sysfsdev);
-    subsys = realpath(tmp, NULL);
-    is_mdev = subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);
-    free(subsys);
-
+    vfio_set_mdev(vbasedev);
+    is_mdev = vbasedev->mdev;

replace with :

  vbasedev->mdev = vfio_device_is_mdev(vbasedev);

and use vbasedev->mdev instead of is_mdev where needed.


Thanks,

C.




      trace_vfio_mdev(vbasedev->name, is_mdev);
if (vbasedev->ram_block_discard_allowed && !is_mdev) {




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