On 28/01/2016 19:54, Peter Maydell wrote: > 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 <peter.mayd...@linaro.org> > --- > 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 >
Sorry, this missed today's pull request. The patch is a fine improvement, feel free to apply it directly. Paolo