diff options
| -rw-r--r-- | docs/vfio-ap.txt | 61 |
1 files changed, 56 insertions, 5 deletions
diff --git a/docs/vfio-ap.txt b/docs/vfio-ap.txt index 1233968..8cd060a 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 +561,54 @@ 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 virtual machine's ap-bus, so a +vfio-ap device can be hot plugged if and only if no vfio-ap device is attached +to the bus already, whether via the QEMU command line or a prior hot plug +action. + +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 to which AP resources to be used by the guest have been assigned. + +Note that on Linux guests, the AP devices will be created in the +/sys/bus/ap/devices directory 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: + +* A vfio-ap device has already been attached to the virtual machine's ap-bus. + +* 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 a vfio-ap device +has been attached to the virtual machine's ap-bus via the QEMU command line +or a prior hot plug action. + +To hot unplug a vfio-ap device, use the QEMU device_del command: + + (qemu) device_del vfio-ap,sysfsdev="$path-to-mdev" + + Where $path-to-mdev is the same as the path specified when the vfio-ap + device was attached to the virtual machine's ap-bus. + +On a Linux guest, 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 when the vfio-ap device was attached to +the virtual machine's ap-bus. + Example: Configure AP Matrixes for Three Linux Guests: ===================================================== Let's now provide an example to illustrate how KVM guests may be given @@ -819,7 +866,11 @@ 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. |