Let's update the vfio-ap.txt document to include the hot plug/unplug
support introduced in this patch set.
Signed-off-by: Tony Krowiak <akrow...@linux.ibm.com>
---
docs/vfio-ap.txt | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 53 insertions(+), 5 deletions(-)
diff --git a/docs/vfio-ap.txt b/docs/vfio-ap.txt
index 12339684cd52..fae40f218620 100644
--- a/docs/vfio-ap.txt
+++ b/docs/vfio-ap.txt
@@ -440,8 +440,7 @@ unassign_control_domain
'unassign_domain' file. This may be done multiple times to unassign more
than
one control domain.
-Notes: Hot plug/unplug is not currently supported for mediated AP matrix
-devices, so no changes to the AP matrix will be allowed while a guest using
+Notes: No changes to the AP matrix will be allowed while a guest using
the mediated matrix device is running. Attempts to assign an adapter,
domain or control domain will be rejected and an error (EBUSY) returned.
@@ -562,6 +561,51 @@ facilities:
for guest usage, no AP devices can be made accessible to a
guest started without APFT installed.
+Hot plug a vfio-ap device into a running guest:
+==============================================
+Only one vfio-ap device can be attached to the guest's ap-bus, so a vfio-ap
+device can be hot plugged if and only if the
+'-device vfio-ap,sysfsdev=$path-to-mdev' option was NOT specified on the QEMU
+command line when the guest was started.
+
+To hot plug a vfio-ap device, use the QEMU device_add command:
+
+ (qemu) device_add vfio-ap,sysfsdev="$path-to-mdev"
+
+ Where the '$path-to-mdev' value specifies the absolute path to a mediated
+ device configured with an AP matrix identifying the AP resources assigned
+ to the guest.
+
+The AP devices will be created in the /sys/bus/ap/devices directory on the
+guest when the AP bus subsequently performs its periodic scan, so there may be
+a short delay before the AP devices are accessible on the guest.
+
+The command will fail if:
+
+* The KVM guest was started with the '-device vfio-ap,sysfs=$path-to-mdev'
+ QEMU command line option.
+
+* The CPU model features for controlling guest access to AP facilities are not
+ enabled (see 'CPU model features' subsection in the previous section).
+
+Hot unplug a vfio-ap device from a running guest:
+================================================
+A vfio-ap device can be unplugged from a running KVM guest if the
+'-device vfio-ap,sysfsdev=$path-to-mdev' option was specified on the QEMU
+command line when the guest was started.
+
+To hot unplug a vfio-ap device, use the QEMU device_del command:
+
+ (qemu) device_del vfio-ap,sysfsdev="$path-to-mdev"
+
+The AP devices will be removed from the /sys/bus/ap/devices directory on the
+guest when the AP bus subsequently performs its periodic scan, so there may be
+a short delay before the AP devices are no longer accessible by the guest.
+
+The command will fail if the $path-to-mdev specified on the device_del command
+does not match the value specified on the '-device vfio-ap,sysfs=$path-to-mdev'
+QEMU command line used to start the guest.
+
Example: Configure AP Matrixes for Three Linux Guests:
=====================================================
Let's now provide an example to illustrate how KVM guests may be given
@@ -819,7 +863,11 @@ Limitations
assigned lest the host be given access to the private data of the AP queue
device, such as a private key configured specifically for the guest.
-* Dynamically modifying the AP matrix for a running guest (which would amount
to
- hot(un)plug of AP devices for the guest) is currently not supported
+* Dynamically assigning AP resources to or unassigning AP resources from a
+ mediated matrix device - see 'Configuring an AP matrix for a linux guest'
+ section above - while a running guest is using it is currently not supported.
-* Live guest migration is not supported for guests using AP devices.
+* Live guest migration is not supported for guests using AP devices. If a guest
+ is using AP devices, the vfio-ap device configured for the guest must be
+ unplugged before migrating the guest (see 'Hot unplug a vfio-ap device from a
+ running guest' section above.
--
2.7.4
