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Re: [Qemu-devel] [PATCH] docs/memory.txt: Improve list of different memo
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] docs/memory.txt: Improve list of different memory regions |
Date: |
Mon, 8 Feb 2016 18:47:20 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 |
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 <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
>
Sorry, this missed today's pull request. The patch is a fine
improvement, feel free to apply it directly.
Paolo
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