include/hw/boards.h: Document memory_region_allocate_system_memory()
Add a documentation comment for memory_region_allocate_system_memory(). In particular, the reason for this function's existence and the requirement on board code to call it exactly once are non-obvious. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 1499438577-7674-2-git-send-email-peter.maydell@linaro.org
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#include "qom/object.h"
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#include "qom/cpu.h"
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/**
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* memory_region_allocate_system_memory - Allocate a board's main memory
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* @mr: the #MemoryRegion to be initialized
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* @owner: the object that tracks the region's reference count
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* @name: name of the memory region
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* @ram_size: size of the region in bytes
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*
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* This function allocates the main memory for a board model, and
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* initializes @mr appropriately. It also arranges for the memory
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* to be migrated (by calling vmstate_register_ram_global()).
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*
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* Memory allocated via this function will be backed with the memory
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* backend the user provided using "-mem-path" or "-numa node,memdev=..."
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* if appropriate; this is typically used to cause host huge pages to be
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* used. This function should therefore be called by a board exactly once,
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* for the primary or largest RAM area it implements.
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*
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* For boards where the major RAM is split into two parts in the memory
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* map, you can deal with this by calling memory_region_allocate_system_memory()
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* once to get a MemoryRegion with enough RAM for both parts, and then
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* creating alias MemoryRegions via memory_region_init_alias() which
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* alias into different parts of the RAM MemoryRegion and can be mapped
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* into the memory map in the appropriate places.
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*
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* Smaller pieces of memory (display RAM, static RAMs, etc) don't need
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* to be backed via the -mem-path memory backend and can simply
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* be created via memory_region_init_ram().
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*/
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void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
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const char *name,
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uint64_t ram_size);
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