docs: rSTify ppc-spapr-hcalls.txt

Signed-off-by: Leonardo Garcia <lagarcia@br.ibm.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
[ clg: - replaced lingua by terminology
       - add a new line at EOF ]
Message-Id: <e20319dcf0ec37bedd915c740c3813eb0e58ead4.1638982486.git.lagarcia@br.ibm.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

1 files changed, 57 insertions, 35 deletions

diff --git a/docs/specs/ppc-spapr-hcalls.txt b/docs/specs/ppc-spapr-hcalls.txt
index 93fe3da91b..28daf9734a 100644
--- a/docs/specs/ppc-spapr-hcalls.txt
+++ b/docs/specs/ppc-spapr-hcalls.txt
@@ -1,9 +1,15 @@
-When used with the "pseries" machine type, QEMU-system-ppc64 implements
-a set of hypervisor calls using a subset of the server "PAPR" specification
-(IBM internal at this point), which is also what IBM's proprietary hypervisor
-adheres too.
+sPAPR hypervisor calls
+----------------------
 
-The subset is selected based on the requirements of Linux as a guest.
+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 document (LoPAR)
+<https://cdn.openpowerfoundation.org/wp-content/uploads/2020/07/LoPAR-20200812.pdf>`_.
+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
@@ -12,13 +18,14 @@ 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)
+H_RTAS (0xf000)
+^^^^^^^^^^^^^^^
 
-RTAS 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 to provide various services that aren't performance
-sensitive.
+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
@@ -26,22 +33,25 @@ 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
+  ``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_SUCCESS``: Successfully called the RTAS function (RTAS result will have
+  been stored in the parameter block).
 
-- H_LOGICAL_MEMOP (0xf001)
+  ``H_PARAMETER``: Unknown token.
 
-When the guest runs in "real mode" (in powerpc lingua this means
-with MMU disabled, ie guest effective == guest physical), it only
-has access to a subset of memory and no IOs.
+H_LOGICAL_MEMOP (0xf001)
+^^^^^^^^^^^^^^^^^^^^^^^^
 
-PAPR provides a set of hypervisor calls to perform cacheable or
+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.
 
@@ -58,21 +68,33 @@ 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
-        0 = 1 byte
-        1 = 2 bytes
-        2 = 4 bytes
-        3 = 8 bytes
-  r7: Number of elements
-  r8: Operation
-        0 = copy
-        1 = xor
+  ``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
+  ``H_SUCCESS``: Success.
 
+  ``H_PARAMETER``: Invalid argument.