Re: [PATCH v2 2/2] accel/tcg: Make probe_access() a generic TCG helper

[Richard Henderson]

On 6/19/23 11:19, Philippe Mathieu-Daudé wrote:
> +
> +void HELPER(probe_access)(CPUArchState *env, uint64_t ptr,
> +                          uint32_t access_type, uint32_t mmu_idx,
> +                          uint32_t size)
> +{
> +    uint32_t in_page = -((uint32_t)ptr | TARGET_PAGE_SIZE);
> +    uintptr_t ra = GETPC();
> +
> +    if (likely(size <= in_page)) {
> +        probe_access(env, ptr, size, access_type, mmu_idx, ra);
> +    } else {
> +        probe_access(env, ptr, in_page, access_type, mmu_idx, ra);
> +        probe_access(env, ptr + in_page, size - in_page,
> +                     access_type, mmu_idx, ra);
> +    }
> +}

This works if and only if size is <= TARGET_PAGE_SIZE.
This should probably have been documented for Arm, but
should definitely be documented for its new location.

It looks like this could be used for

hexagon: HELPER(probe_noshuf_load)
s390x/tcg/mem_helper.c:void HELPER(probe_write_access)

Although s390x is written to handle much larger SIZE, the maximum that it will ever issue 
is 16 * 16 = 256 for op_vstm.  But it also handles target-specific address wrap at the end 
of the address space, which the above does not.

So perhaps it's not worth moving this after all?


r~