Re: [Qemu-devel] physical memory address in guest (from his point of view)

[Peter Maydell]

On 24 April 2015 at 09:46, Catalin Vasile <address@hidden> wrote:
> Does a physical memory address in a guest points to the same memory as qemu?
> For example: if I have a physical pointer 0x34 in the guest, does it
> point to the same location that qemu points with 0x34 address?

As an additional point to Paolo's answer, consider that:
 (1) a guest physical address alone may not be sufficient to identify
the host memory/device [consider ARM TrustZone where you also need
to know the Secure/NonSecure attribute]
 (2) a guest physical address may not map to anything on the host
 (3) a guest physical address may map to an emulated device, not
host RAM
 (4) multiple guest physical addresses may map to a single host
RAM address [if the RAM is aliased to multiple physaddrs]
 (5) host memory that is part of the machine model may not be
mapped to any guest physical address [consider a device with a
block of "ram" accessed via set-address/write-data commands, or
a PCI device with a BAR that has been temporarily unmapped by the guest]

There are a lot of odd cases that the memory system infrastructure
deals with for you...

-- PMM