Re: [PATCH for-6.0 v2 5/5] target/arm: Make M-profile VTOR loads on reset handle memory aliasing

[Richard Henderson <richard.henderson@linaro.org>]

On 3/18/21 11:48 AM, Peter Maydell wrote:
> For Arm M-profile CPUs, on reset the CPU must load its initial PC and
> SP from a vector table in guest memory.  Because we can't guarantee
> reset ordering, we have to handle the possibility that the ROM blob
> loader's reset function has not yet run when the CPU resets, in which
> case the data in an ELF file specified by the user won't be in guest
> memory to be read yet.
> 
> We work around the reset ordering problem by checking whether the ROM
> blob loader has any data for the address where the vector table is,
> using rom_ptr().  Unfortunately this does not handle the possibility
> of memory aliasing.  For many M-profile boards, memory can be
> accessed via multiple possible physical addresses; if the board has
> the vector table at address X but the user's ELF file loads data via
> a different address Y which is an alias to the same underlying guest
> RAM then rom_ptr() will not find it.
> 
> Use the new rom_ptr_for_as() function, which deals with memory
> aliasing when locating a relevant ROM blob.
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
>   target/arm/cpu.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~