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vfio: add region info cache

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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.johnson@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250507152020.1254632-12-john.levon@nutanix.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
This commit is contained in:
John Levon 2025-05-07 16:20:16 +01:00 • committed by Cédric Le Goater
parent 38bf025d0d
commit 95cdb02451
6 changed files with 31 additions and 18 deletions
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25
hw/vfio/device.c
View file

@ -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;