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Re: [Qemu-devel] [PATCH 0/2] [RFC] 64-bit io paths
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH 0/2] [RFC] 64-bit io paths |
Date: |
Fri, 28 May 2010 22:03:58 +0100 |
[Hit send too early on previous mail...]
> The basic device interface looks like
> ...
> +
> +/* Register a memory region at START_ADDR/SIZE. The REGION structure will
> + be initialized appropriately for DEV using CB as the operation set. */
> +extern void cpu_register_memory_region(MemoryRegion *region,
> + const MemoryCallbackInfo *cb,
> + target_phys_addr_t start_addr,
> + target_phys_addr_t size);
> +
> +/* Unregister a memory region. */
> +extern void cpu_unregister_memory_region(MemoryRegion *);
> +
> +/* Allocate ram for use with cpu_register_memory_region. */
> +extern const MemoryCallbackInfo *qemu_ram_alloc_r(ram_addr_t);
> +extern void qemu_ram_free_r(const MemoryCallbackInfo *);
>
> The Basic Idea is that we have a MemoryRegion object that describes
> a contiguous mapping within the guest address space. This object
> needs to handle RAM, ROM and devices. The desire to handle memory
> and devices the same comes from the wish to have PCI device BARs
> show up as plain memory in the TLB as plain memory, and to be able
> to handle all PCI device regions identically within sysbus.
Looks reasonable to me.
I'm tempted to add a DeviceState* argument to cpu_register_memory_region.
This might be informative for debugging, and allow future disjoint bus
support. OTOH it might be more trouble than it's worth.
> I will admit that I do not yet have a good replacement for IO_MEM_ROMD,
> or toggling the read-only bit on a RAM region.
I suggest adding a MemoryCallbackInfo* argument to qemu_ram_alloc_r.
If NULL this allocates a regular RAM block. if non-null it allocates a hybrid
ROM/IO block using the specified callbacks for IO accesses. Then introduce a
function that allows a device to switch a mapping between ROM and IO modes.
Likewise to make a mapping of a RAM region readonly.
Paul