11681b79b1
The PowerNV L0 currently pushes the OS xive context when running a vCPU, regardless of whether it is running a nested guest. The problem is that xive OS ring interrupts will be delivered while the L2 is running. At the moment, by default, the L2 guest runs with LPCR[LPES]=0, which actually makes external interrupts go to the L0. That causes the L2 to exit and the interrupt taken or injected into the L1, so in some respects this behaves like an escalation. It's not clear if this was deliberate or not, there's no comment about it and the L1 is actually allowed to clear LPES in the L2, so it's confusing at best. When the L2 is running, the L1 is essentially in a ceded state with respect to external interrupts (it can't respond to them directly and won't get scheduled again absent some additional event). So the natural way to solve this is when the L0 handles a H_ENTER_NESTED hypercall to run the L2, have it arm the escalation interrupt and don't push the L1 context while running the L2. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20220303053315.1056880-6-npiggin@gmail.com
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.