Re: [Qemu-devel] [PATCH v4 2/2] hw/integratorcp: Simplify flash remap code

[Peter Maydell]

On 7 January 2012 04:40, Andreas Färber <address@hidden> wrote:
> I noticed you're dropping a comment about tlb_flush(). Is that because
> it was dead code, or does the Memory API take care of it for us?
> (I assume the former because memory_region_set_enabled() does not take a
> CPUState* to operate on.)

Arranging for a tlb_flush if needed has to be the Memory API's
problem, because everything that uses the memory API to rearrange
the view of the address space has exactly the same requirement that
anything else in QEMU has to be told it may need to redo any caching
data structure it has set up. In particular, this doesn't apply just
for a single CPUState* -- in a multicore system every CPU has to be
made aware that the world has changed, not just the one which
happened to do the store to the "remap the flash" register.
Also the memory API is the only thing that knows whether the region
was already enabled (ie this is a no-op), whether some other region
is overlapping so in fact it makes no difference whether we enable
or disable this one, etc etc).

So basically I dropped that line because it was a bit of commented
out code with a ??? marker appended, and the device layer is the
wrong place to be trying to solve the issue it was gesturing at.

-- PMM