31a88c82b4
The EQ page is allocated by the guest and then passed to the hypervisor with the H_INT_SET_QUEUE_CONFIG hcall. A reference is taken on the page before handing it over to the HW. This reference is dropped either when the guest issues the H_INT_RESET hcall or when the KVM device is released. But, the guest can legitimately call H_INT_SET_QUEUE_CONFIG several times, either to reset the EQ (vCPU hot unplug) or to set a new EQ (guest reboot). In both cases the existing EQ page reference is leaked because we simply overwrite it in the XIVE queue structure without calling put_page(). This is especially visible when the guest memory is backed with huge pages: start a VM up to the guest userspace, either reboot it or unplug a vCPU, quit QEMU. The leak is observed by comparing the value of HugePages_Free in /proc/meminfo before and after the VM is run. Ideally we'd want the XIVE code to handle the EQ page de-allocation at the platform level. This isn't the case right now because the various XIVE drivers have different allocation needs. It could maybe worth introducing hooks for this purpose instead of exposing XIVE internals to the drivers, but this is certainly a huge work to be done later. In the meantime, for easier backport, fix both vCPU unplug and guest reboot leaks by introducing a wrapper around xive_native_configure_queue() that does the necessary cleanup. Reported-by: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com> Cc: stable@vger.kernel.org # v5.2 Fixes: 13ce3297c576 ("KVM: PPC: Book3S HV: XIVE: Add controls for the EQ configuration") Signed-off-by: Cédric Le Goater <clg@kaod.org> Signed-off-by: Greg Kurz <groug@kaod.org> Tested-by: Lijun Pan <ljp@linux.ibm.com> Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.