99 lines
3.1 KiB
ReStructuredText
99 lines
3.1 KiB
ReStructuredText
======================
|
|
sPAPR hypervisor calls
|
|
======================
|
|
|
|
When used with the ``pseries`` machine type, ``qemu-system-ppc64`` implements
|
|
a set of hypervisor calls (a.k.a. hcalls) defined in the Linux on Power
|
|
Architecture Reference ([LoPAR]_) document. This document is a subset of the
|
|
Power Architecture Platform Reference (PAPR+) specification (IBM internal only),
|
|
which is what PowerVM, the IBM proprietary hypervisor, adheres to.
|
|
|
|
The subset in LoPAR is selected based on the requirements of Linux as a guest.
|
|
|
|
In addition to those calls, we have added our own private hypervisor
|
|
calls which are mostly used as a private interface between the firmware
|
|
running in the guest and QEMU.
|
|
|
|
All those hypercalls start at hcall number 0xf000 which correspond
|
|
to an implementation specific range in PAPR.
|
|
|
|
``H_RTAS (0xf000)``
|
|
===================
|
|
|
|
RTAS stands for Run-Time Abstraction Sercies and is a set of runtime services
|
|
generally provided by the firmware inside the guest to the operating system. It
|
|
predates the existence of hypervisors (it was originally an extension to Open
|
|
Firmware) and is still used by PAPR and LoPAR to provide various services that
|
|
are not performance sensitive.
|
|
|
|
We currently implement the RTAS services in QEMU itself. The actual RTAS
|
|
"firmware" blob in the guest is a small stub of a few instructions which
|
|
calls our private H_RTAS hypervisor call to pass the RTAS calls to QEMU.
|
|
|
|
Arguments:
|
|
|
|
``r3``: ``H_RTAS (0xf000)``
|
|
|
|
``r4``: Guest physical address of RTAS parameter block.
|
|
|
|
Returns:
|
|
|
|
``H_SUCCESS``: Successfully called the RTAS function (RTAS result will have
|
|
been stored in the parameter block).
|
|
|
|
``H_PARAMETER``: Unknown token.
|
|
|
|
``H_LOGICAL_MEMOP (0xf001)``
|
|
============================
|
|
|
|
When the guest runs in "real mode" (in powerpc terminology this means with MMU
|
|
disabled, i.e. guest effective address equals to guest physical address), it
|
|
only has access to a subset of memory and no I/Os.
|
|
|
|
PAPR and LoPAR provides a set of hypervisor calls to perform cacheable or
|
|
non-cacheable accesses to any guest physical addresses that the
|
|
guest can use in order to access IO devices while in real mode.
|
|
|
|
This is typically used by the firmware running in the guest.
|
|
|
|
However, doing a hypercall for each access is extremely inefficient
|
|
(even more so when running KVM) when accessing the frame buffer. In
|
|
that case, things like scrolling become unusably slow.
|
|
|
|
This hypercall allows the guest to request a "memory op" to be applied
|
|
to memory. The supported memory ops at this point are to copy a range
|
|
of memory (supports overlap of source and destination) and XOR which
|
|
is used by our SLOF firmware to invert the screen.
|
|
|
|
Arguments:
|
|
|
|
``r3 ``: ``H_LOGICAL_MEMOP (0xf001)``
|
|
|
|
``r4``: Guest physical address of destination.
|
|
|
|
``r5``: Guest physical address of source.
|
|
|
|
``r6``: Individual element size, defined by the binary logarithm of the
|
|
desired size. Supported values are:
|
|
|
|
``0`` = 1 byte
|
|
|
|
``1`` = 2 bytes
|
|
|
|
``2`` = 4 bytes
|
|
|
|
``3`` = 8 bytes
|
|
|
|
``r7``: Number of elements.
|
|
|
|
``r8``: Operation. Supported values are:
|
|
|
|
``0``: copy
|
|
|
|
``1``: xor
|
|
|
|
Returns:
|
|
|
|
``H_SUCCESS``: Success.
|
|
|
|
``H_PARAMETER``: Invalid argument.
|