Re: [PATCH v3 11/15] vfio: add region info cache

Cédric Le Goater Fri, 09 May 2025 03:10:57 -0700

On 5/7/25 17:20, John Levon wrote:

Instead of requesting region information on demand with
VFIO_DEVICE_GET_REGION_INFO, maintain a cache: this will become
necessary for performance for vfio-user, where this call becomes a
message over the control socket, so is of higher overhead than the
traditional path.


We will also need it to generalize region accesses, as that means we
can't use ->config_offset for configuration space accesses, but must
look up the region offset (if relevant) each time.

Originally-by: John Johnson <john.g.john...@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimts...@oracle.com>
Signed-off-by: Jagannathan Raman <jag.ra...@oracle.com>
Signed-off-by: John Levon <john.le...@nutanix.com>



Reviewed-by: Cédric Le Goater <c...@redhat.com>

Thanks,

C.

---
  include/hw/vfio/vfio-device.h |  1 +
  hw/vfio/ccw.c                 |  5 -----
  hw/vfio/device.c              | 25 +++++++++++++++++++++----
  hw/vfio/igd.c                 | 10 +++++-----
  hw/vfio/pci.c                 |  6 +++---
  hw/vfio/region.c              |  2 +-
  6 files changed, 31 insertions(+), 18 deletions(-)

diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h
index 7e1e81e76b..4fff3dcee3 100644
--- a/include/hw/vfio/vfio-device.h
+++ b/include/hw/vfio/vfio-device.h
@@ -83,6 +83,7 @@ typedef struct VFIODevice {
      IOMMUFDBackend *iommufd;
      VFIOIOASHwpt *hwpt;
      QLIST_ENTRY(VFIODevice) hwpt_next;
+    struct vfio_region_info **reginfo;
  } VFIODevice;

struct VFIODeviceOps {

diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
index ab3fabf991..cea9d6e005 100644
--- a/hw/vfio/ccw.c
+++ b/hw/vfio/ccw.c
@@ -504,7 +504,6 @@ static bool vfio_ccw_get_region(VFIOCCWDevice *vcdev, Error 
**errp)

vcdev->io_region_offset = info->offset;

      vcdev->io_region = g_malloc0(info->size);
-    g_free(info);

/* check for the optional async command region */

      ret = vfio_device_get_region_info_type(vdev, VFIO_REGION_TYPE_CCW,
@@ -517,7 +516,6 @@ static bool vfio_ccw_get_region(VFIOCCWDevice *vcdev, Error 
**errp)
          }
          vcdev->async_cmd_region_offset = info->offset;
          vcdev->async_cmd_region = g_malloc0(info->size);
-        g_free(info);
      }

ret = vfio_device_get_region_info_type(vdev, VFIO_REGION_TYPE_CCW,

@@ -530,7 +528,6 @@ static bool vfio_ccw_get_region(VFIOCCWDevice *vcdev, Error 
**errp)
          }
          vcdev->schib_region_offset = info->offset;
          vcdev->schib_region = g_malloc(info->size);
-        g_free(info);
      }

ret = vfio_device_get_region_info_type(vdev, VFIO_REGION_TYPE_CCW,

@@ -544,7 +541,6 @@ static bool vfio_ccw_get_region(VFIOCCWDevice *vcdev, Error 
**errp)
          }
          vcdev->crw_region_offset = info->offset;
          vcdev->crw_region = g_malloc(info->size);
-        g_free(info);
      }

return true;

@@ -554,7 +550,6 @@ out_err:
      g_free(vcdev->schib_region);
      g_free(vcdev->async_cmd_region);
      g_free(vcdev->io_region);
-    g_free(info);
      return false;
  }

diff --git a/hw/vfio/device.c b/hw/vfio/device.c

index 40a196bfb9..77b0675abe 100644
--- a/hw/vfio/device.c
+++ b/hw/vfio/device.c
@@ -202,6 +202,12 @@ int vfio_device_get_region_info(VFIODevice *vbasedev, int 
index,
      size_t argsz = sizeof(struct vfio_region_info);
      int ret;

+ /* check cache */

+    if (vbasedev->reginfo[index] != NULL) {
+        *info = vbasedev->reginfo[index];
+        return 0;
+    }
+
      *info = g_malloc0(argsz);

(*info)->index = index;

@@ -222,6 +228,9 @@ retry:
          goto retry;
      }

+ /* fill cache */

+    vbasedev->reginfo[index] = *info;
+
      return 0;
  }

@@ -240,7 +249,6 @@ int vfio_device_get_region_info_type(VFIODevice *vbasedev, uint32_t type,hdr = vfio_get_region_info_cap(*info, VFIO_REGION_INFO_CAP_TYPE);

          if (!hdr) {
-            g_free(*info);
              continue;
          }

@@ -252,8 +260,6 @@ int vfio_device_get_region_info_type(VFIODevice *vbasedev, uint32_t type,

          if (cap_type->type == type && cap_type->subtype == subtype) {
              return 0;
          }
-
-        g_free(*info);
      }

*info = NULL;

@@ -262,7 +268,7 @@ int vfio_device_get_region_info_type(VFIODevice *vbasedev, 
uint32_t type,

bool vfio_device_has_region_cap(VFIODevice *vbasedev, int region, uint16_t cap_type)

  {
-    g_autofree struct vfio_region_info *info = NULL;
+    struct vfio_region_info *info = NULL;
      bool ret = false;

if (!vfio_device_get_region_info(vbasedev, region, &info)) {

@@ -435,10 +441,21 @@ void vfio_device_prepare(VFIODevice *vbasedev, 
VFIOContainerBase *bcontainer,
      QLIST_INSERT_HEAD(&bcontainer->device_list, vbasedev, container_next);

QLIST_INSERT_HEAD(&vfio_device_list, vbasedev, global_next);

+
+    vbasedev->reginfo = g_new0(struct vfio_region_info *,
+                               vbasedev->num_regions);
  }

void vfio_device_unprepare(VFIODevice *vbasedev)

  {
+    int i;
+
+    for (i = 0; i < vbasedev->num_regions; i++) {
+        g_free(vbasedev->reginfo[i]);
+    }
+    g_free(vbasedev->reginfo);
+    vbasedev->reginfo = NULL;
+
      QLIST_REMOVE(vbasedev, container_next);
      QLIST_REMOVE(vbasedev, global_next);
      vbasedev->bcontainer = NULL;
diff --git a/hw/vfio/igd.c b/hw/vfio/igd.c
index 3ee1a73b57..e7952d15a0 100644
--- a/hw/vfio/igd.c
+++ b/hw/vfio/igd.c
@@ -349,8 +349,8 @@ static int vfio_pci_igd_lpc_init(VFIOPCIDevice *vdev,

static bool vfio_pci_igd_setup_lpc_bridge(VFIOPCIDevice *vdev, Error **errp)

  {
-    g_autofree struct vfio_region_info *host = NULL;
-    g_autofree struct vfio_region_info *lpc = NULL;
+    struct vfio_region_info *host = NULL;
+    struct vfio_region_info *lpc = NULL;
      PCIDevice *lpc_bridge;
      int ret;

@@ -510,7 +510,7 @@ void vfio_probe_igd_bar0_quirk(VFIOPCIDevice *vdev, int nr)static bool vfio_pci_igd_config_quirk(VFIOPCIDevice *vdev, Error **errp)

  {
-    g_autofree struct vfio_region_info *opregion = NULL;
+    struct vfio_region_info *opregion = NULL;
      int ret, gen;
      uint64_t gms_size = 0;
      uint64_t *bdsm_size;
@@ -551,7 +551,7 @@ static bool vfio_pci_igd_config_quirk(VFIOPCIDevice *vdev, 
Error **errp)
           * - OpRegion
           * - Same LPC bridge and Host bridge VID/DID/SVID/SSID as host
           */
-        g_autofree struct vfio_region_info *rom = NULL;
+        struct vfio_region_info *rom = NULL;

legacy_mode_enabled = true;

          info_report("IGD legacy mode enabled, "
@@ -681,7 +681,7 @@ error:
   */
  static bool vfio_pci_kvmgt_config_quirk(VFIOPCIDevice *vdev, Error **errp)
  {
-    g_autofree struct vfio_region_info *opregion = NULL;
+    struct vfio_region_info *opregion = NULL;
      int gen;

if (!vfio_pci_is(vdev, PCI_VENDOR_ID_INTEL, PCI_ANY_ID) ||

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index da2ffc9bf3..9136cf52c8 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -883,8 +883,8 @@ static void vfio_update_msi(VFIOPCIDevice *vdev)

static void vfio_pci_load_rom(VFIOPCIDevice *vdev)

  {
-    g_autofree struct vfio_region_info *reg_info = NULL;
      VFIODevice *vbasedev = &vdev->vbasedev;
+    struct vfio_region_info *reg_info = NULL;
      uint64_t size;
      off_t off = 0;
      ssize_t bytes;
@@ -2710,7 +2710,7 @@ static VFIODeviceOps vfio_pci_ops = {
  bool vfio_populate_vga(VFIOPCIDevice *vdev, Error **errp)
  {
      VFIODevice *vbasedev = &vdev->vbasedev;
-    g_autofree struct vfio_region_info *reg_info = NULL;
+    struct vfio_region_info *reg_info = NULL;
      int ret;

ret = vfio_device_get_region_info(vbasedev, VFIO_PCI_VGA_REGION_INDEX, &reg_info);

@@ -2775,7 +2775,7 @@ bool vfio_populate_vga(VFIOPCIDevice *vdev, Error **errp)
  static bool vfio_populate_device(VFIOPCIDevice *vdev, Error **errp)
  {
      VFIODevice *vbasedev = &vdev->vbasedev;
-    g_autofree struct vfio_region_info *reg_info = NULL;
+    struct vfio_region_info *reg_info = NULL;
      struct vfio_irq_info irq_info;
      int i, ret = -1;

diff --git a/hw/vfio/region.c b/hw/vfio/region.c

index 04bf9eb098..ef2630cac3 100644
--- a/hw/vfio/region.c
+++ b/hw/vfio/region.c
@@ -182,7 +182,7 @@ static int vfio_setup_region_sparse_mmaps(VFIORegion 
*region,
  int vfio_region_setup(Object *obj, VFIODevice *vbasedev, VFIORegion *region,
                        int index, const char *name)
  {
-    g_autofree struct vfio_region_info *info = NULL;
+    struct vfio_region_info *info = NULL;
      int ret;

ret = vfio_device_get_region_info(vbasedev, index, &info);

Re: [PATCH v3 11/15] vfio: add region info cache

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