Re: [PATCH for-6.0 0/2] arm: Make M-profile VTOR loads on reset handle memory aliasing

[Peter Maydell]

On Sat, 13 Mar 2021 at 19:05, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 3/12/21 12:59 PM, Peter Maydell wrote:
> > On Fri, 12 Mar 2021 at 17:29, Peter Maydell <peter.maydell@linaro.org> 
> > wrote:
> >> This series handles the possibility of aliasing by iterating through
> >> the whole FlatView of the CPU's address space checking for other
> >> mappings of the MemoryRegion corresponding to the location of the
> >> vector table.  If we find any aliases we use rom_ptr() to see if the
> >> ROM blob loader has any data there.
> >
> > The other possible place we could put this code would be
> > to put it into rom_ptr() itself. You'd have to change the
> > callsites to pass an AddressSpace to rom_ptr(), but really
> > we ought to do that anyway, because a Rom has an AddressSpace
> > that we should be checking as well as the address.
>
> I like this as the solution.

I realized that checking against the Rom's AddressSpace
is likely to be a bad plan, though -- in some cases the AS is
used to allow the loader to say "load this image to AS
such-and-such", and we don't want to fail to find the ROM
blob because the rom_ptr() code is reading it from a different
AS that is an alternate view onto the same actual MemoryRegions
(eg Secure vs NonSecure and the RAM is in the same place.)

thanks
-- PMM