On 1/7/25 2:06 PM, Alex Williamson wrote:
On Tue, 7 Jan 2025 13:43:49 -0500
Rorie Reyes <rre...@linux.ibm.com> wrote:
This patch series creates and registers a handler that is called when
userspace is notified by the kernel that a guest's AP configuration has
changed. The handler in turn notifies the guest that its AP configuration
has changed. This allows the guest to immediately respond to AP
configuration changes rather than relying on polling or some other
inefficient mechanism for detecting config changes.
Why are configuration changes to the device allowed while the device is
in use?
Would a uevent be considered an inefficient mechanism? Why?
Thanks,
Alex
Hey Alex,
Sorry for the long delay, but to answer your question, the VFIO device
is typically used to pass through a single I/O
device, like a VGPU or PCI device. VFIO allows direct access to the
memory of the underlying device to perofrm the I/O.
Our VFIO device does not follow that model and it represents a guest's
AP configuration, not an individual AP device. Granting
guest access to AP devices in the configuration is controlled outside of
the VFIO. The purpose of the mdev is to provide
a means for specifying the AP configuration for the guest. When the mdev
is attached to the guest, the vfio_ap device driver
set the AP configuration assigned to the mdev into the control blocks
used to start the guest.
