Re: [Qemu-devel] [PATCH] Add e500 instructions dcblc, dcbtls and dcbtstl as no-op

[Scott Wood]

On Thu, 30 Jun 2011 23:34:37 +0200
Alexander Graf <address@hidden> wrote:

> We could just keep an internal counter that memorizes how much memory is 
> locked and sets the bit after exceeding the fake cache size.

And keep track of unlocks, decrementing the counter only if the address was
already locked...  seems better to keep it simple and just be honest about
the failure until a real need for trickery arises.

> The only problem I could see remaining is that CAR could potentially fail, as 
> it can access addresses in cache directly that don't have to have underlying 
> RAM mapped. However, I'd hope that only firmware does this and we usually 
> don't execute real firmware in qemu :)

This is a case where it would be nice for the guest to see the failure
indication, if we're lucky enough that it bothers to check.

But yeah, it's unlikely to happen outside of firmware.

> Also, lock set instructions seem to raise DSIs, so we need to generate some 
> loads that don't go anywhere.

Yes.

Note that dcbtstls is treated as a store, which is a little trickier.

-Scott