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

[Peter Maydell <peter.maydell@linaro.org>]

On Fri, 12 Mar 2021 at 20:17, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
> Your solution seems generic, and the problem is not resticted
> to Cortex-M:
>
> $ git grep rom_ptr target
> target/arm/cpu.c:334:        rom = rom_ptr(vecbase, 8);
> target/rx/cpu.c:61:    resetvec = rom_ptr(0xfffffffc, 4);
>
> Some thoughs:
> - make find_rom_for_addr() generic ("hw/loader.h" again?)
> - poison rom_ptr() under target/ to restrict it to hw/

This problem isn't specific to code in target/, that's just
the particular case I care about. The uses in hw/ are mostly
in board init code, which (like cpu reset code) runs before
the rom blob reset function, and so wants to directly look
at the blob data. If a board has multiple aliases for a piece
of RAM then rom_ptr() will cause problems for code in hw/ too.
The only advantage that uses of rom_ptr() in hw/ have is that
they can know which board model they're running on and so either
(a) be sure that the address they're looking at doesn't have any
aliases elsewhere in the AddressSpace or (b) manually look at
every alias address in turn.

thanks
-- PMM