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Re: [Qemu-devel] Fw:Re:Re: How to access guest memory from qemu device i


From: Peter Maydell
Subject: Re: [Qemu-devel] Fw:Re:Re: How to access guest memory from qemu device internal
Date: Fri, 21 Nov 2014 13:15:15 +0000

On 21 November 2014 09:17, Kaiyuan <address@hidden> wrote:
> Thanks, Greg. It's useful to me. cpu_physical_memory_read()
> looks like a wrapper of translating guest addr to host addr
> Is there a function that translates guest address to host
> physical address?

No, QEMU never deals with host physical addresses at all.
In general there are three address types that might be
in use:
 * guest virtual address
 * guest physical address
 * host virtual address (only relevant if talking to RAM,
     rather than an emulated device)

For devices, the guest within the VM should deal with
converting a virtual address to a guest physical address,
and should write guest physical addresses to the device.
[If you think about real hardware, where the device is
separate from the CPU, there's no way the device can know
about guest virtual addresses, which are handled by the
CPU's built in MMU.]

So the function Greg suggests is the one you want.

-- PMM



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