On 27.06.2023 19:22, Demi Marie Obenour wrote:
When a grant entry is still in use by the remote domain, Linux must put it on a deferred list. Normally, this list is very short, because the PV network and block protocols expect the backend to unmap the grant first. However, Qubes OS's GUI protocol is subject to the constraints of the X Window System, and as such winds up with the frontend unmapping the window first. As a result, the list can grow very large, resulting in a massive memory leak and eventual VM freeze.
To partially solve this problem, make the number of entries that the VM will attempt to free at each iteration tunable. The default is still 10, but it can be overridden at compile-time (via Kconfig), boot-time (via a kernel command-line option), or runtime (via sysfs).
This is Cc: stable because (when combined with appropriate userspace changes) it fixes a severe performance and stability problem for Qubes OS users.
Cc: stable@vger.kernel.org Signed-off-by: Demi Marie Obenour demi@invisiblethingslab.com
Why am I _still_ - after two earlier private questions to the same effect - on the To: list of this submission? Please can you respect other people's time and interests and properly follow patch submission rules, applying common sense when (like has been the case in the past for Linux) those rules result in overly broad sets of people.
Jan