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[Qemu-devel] [PULL 29/32] docs/memory.txt: Improve list of different mem
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 29/32] docs/memory.txt: Improve list of different memory regions |
Date: |
Tue, 9 Feb 2016 13:13:48 +0100 |
From: Peter Maydell <address@hidden>
Improve the part of the memory region documentation which describes
the various different kinds of memory region:
* add the missing types ROM, IOMMU and reservation
* mention the functions used to initialize each type, as a hint
for finding the API docs and examples of use
Signed-off-by: Peter Maydell <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
docs/memory.txt | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/docs/memory.txt b/docs/memory.txt
index 2ceb348..8745f76 100644
--- a/docs/memory.txt
+++ b/docs/memory.txt
@@ -26,14 +26,28 @@ These represent memory as seen from the CPU or a device's
viewpoint.
Types of regions
----------------
-There are four types of memory regions (all represented by a single C type
+There are multiple types of memory regions (all represented by a single C type
MemoryRegion):
- RAM: a RAM region is simply a range of host memory that can be made available
to the guest.
+ You typically initialize these with memory_region_init_ram(). Some special
+ purposes require the variants memory_region_init_resizeable_ram(),
+ memory_region_init_ram_from_file(), or memory_region_init_ram_ptr().
- MMIO: a range of guest memory that is implemented by host callbacks;
each read or write causes a callback to be called on the host.
+ You initialize these with memory_region_io(), passing it a MemoryRegionOps
+ structure describing the callbacks.
+
+- ROM: a ROM memory region works like RAM for reads (directly accessing
+ a region of host memory), but like MMIO for writes (invoking a callback).
+ You initialize these with memory_region_init_rom_device().
+
+- IOMMU region: an IOMMU region translates addresses of accesses made to it
+ and forwards them to some other target memory region. As the name suggests,
+ these are only needed for modelling an IOMMU, not for simple devices.
+ You initialize these with memory_region_init_iommu().
- container: a container simply includes other memory regions, each at
a different offset. Containers are useful for grouping several regions
@@ -45,12 +59,22 @@ MemoryRegion):
can overlay a subregion of RAM with MMIO or ROM, or a PCI controller
that does not prevent card from claiming overlapping BARs.
+ You initialize a pure container with memory_region_init().
+
- alias: a subsection of another region. Aliases allow a region to be
split apart into discontiguous regions. Examples of uses are memory banks
used when the guest address space is smaller than the amount of RAM
addressed, or a memory controller that splits main memory to expose a "PCI
hole". Aliases may point to any type of region, including other aliases,
but an alias may not point back to itself, directly or indirectly.
+ You initialize these with memory_region_init_alias().
+
+- reservation region: a reservation region is primarily for debugging.
+ It claims I/O space that is not supposed to be handled by QEMU itself.
+ The typical use is to track parts of the address space which will be
+ handled by the host kernel when KVM is enabled.
+ You initialize these with memory_region_init_reservation(), or by
+ passing a NULL callback parameter to memory_region_init_io().
It is valid to add subregions to a region which is not a pure container
(that is, to an MMIO, RAM or ROM region). This means that the region
--
2.5.0
[Qemu-devel] [PULL 32/32] qemu-char, io: fix ordering of arguments for UDP socket creation, Paolo Bonzini, 2016/02/09
[Qemu-devel] [PULL 08/32] hw: Add support for LSI SAS1068 (mptsas) device, Paolo Bonzini, 2016/02/09
Re: [Qemu-devel] [PULL v2 00/32] Misc changes for 2016-02-08, Peter Maydell, 2016/02/09