Re: [PATCH] Revert "arm/kvm: add support for MTE"

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

On 5/19/23 07:58, Peter Maydell wrote:
> This reverts commit b320e21c48ce64853904bea6631c0158cc2ef227,
> which accidentally broke TCG, because it made the TCG -cpu max
> report the presence of MTE to the guest even if the board hadn't
> enabled MTE by wiring up the tag RAM. This meant that if the guest
> then tried to use MTE QEMU would segfault accessing the
> non-existent tag RAM:
> 
>      ==346473==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address (pc 0x55f328952a4a bp 0x00000213a400 sp 0x7f7871859b80 T346476)
>      ==346473==The signal is caused by a READ memory access.
>      ==346473==Hint: this fault was caused by a dereference of a high value address (see register values below).  Disassemble the provided pc to learn which register was used.
>          #0 0x55f328952a4a in address_space_to_flatview /mnt/nvmedisk/linaro/qemu-from-laptop/qemu/include/exec/memory.h:1108:12
>          #1 0x55f328952a4a in address_space_translate /mnt/nvmedisk/linaro/qemu-from-laptop/qemu/include/exec/memory.h:2797:31
>          #2 0x55f328952a4a in allocation_tag_mem/mnt/nvmedisk/linaro/qemu-from-laptop/qemu/build/arm-clang/../../target/arm/tcg/mte_helper.c:176:10
>          #3 0x55f32895366c in helper_stgm/mnt/nvmedisk/linaro/qemu-from-laptop/qemu/build/arm-clang/../../target/arm/tcg/mte_helper.c:461:15
>          #4 0x7f782431a293  (<unknown module>)
> 
> It's also not clear that the KVM logic is correct either:
> MTE defaults to on there, rather than being only on if the
> board wants it on.
> 
> Revert the whole commit for now so we can sort out the issues.
> 
> (We didn't catch this in CI because we have no test cases in
> avocado that use guests with MTE support.)
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
> Richard, do you want to apply this to master as a buildfix?

Can do, yes.


r~