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authorPeter Maydell <peter.maydell@linaro.org>2016-02-09 19:34:46 +0000
committerPeter Maydell <peter.maydell@linaro.org>2016-02-09 19:34:46 +0000
commitc9f19dff101e2c2cf3fa3967eceec2833e845e40 (patch)
tree5bcc3ba8281fc7902d3c99bbbf1a7097384c711b /docs
parentf075c89f0a9cb31daf38892371d2822177505706 (diff)
parent150dcd1aed6f9ebcf370dbb9b666e7d7c6d908e2 (diff)
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Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging
* switch to C11 atomics (Alex) * Coverity fixes for IPMI (Corey), i386 (Paolo), qemu-char (Paolo) * at long last, fail on wrong .pc files if -m32 is in use (Daniel) * qemu-char regression fix (Daniel) * SAS1068 device (Paolo) * memory region docs improvements (Peter) * target-i386 cleanups (Richard) * qemu-nbd docs improvements (Sitsofe) * thread-safe memory hotplug (Stefan) # gpg: Signature made Tue 09 Feb 2016 16:09:30 GMT using RSA key ID 78C7AE83 # gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" # gpg: aka "Paolo Bonzini <pbonzini@redhat.com>" * remotes/bonzini/tags/for-upstream: (33 commits) qemu-char, io: fix ordering of arguments for UDP socket creation MAINTAINERS: add all-match entry for qemu-devel@ get_maintainer.pl: fall back to git if only lists are found target-i386: fix PSE36 mode docs/memory.txt: Improve list of different memory regions ipmi_bmc_sim: Add break to correct watchdog NMI check ipmi_bmc_sim: Fix off by one in check. ipmi: do not take/drop iothread lock target-i386: Deconstruct the cpu_T array target-i386: Tidy gen_add_A0_im target-i386: Rewrite leave target-i386: Rewrite gen_enter inline target-i386: Use gen_lea_v_seg in pusha/popa target-i386: Access segs via TCG registers target-i386: Use gen_lea_v_seg in stack subroutines target-i386: Use gen_lea_v_seg in gen_lea_modrm target-i386: Introduce mo_stacksize target-i386: Create gen_lea_v_seg char: fix repeated registration of tcp chardev I/O handlers kvm-all: trace: strerror fixup ... Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Diffstat (limited to 'docs')
-rw-r--r--docs/memory.txt26
1 files changed, 25 insertions, 1 deletions
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