Re: [PATCH v2 20/55] accel/tcg: Report unaligned atomics for user-only

[Philippe Mathieu-Daudé]

Hi Richard,

On 8/3/21 6:14 AM, Richard Henderson wrote:
> Use the newly exposed cpu_unaligned_access for atomic_mmu_lookup,
> which has access to complete alignment info from the TCGMemOpIdx arg.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  accel/tcg/user-exec.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
> index 90d1a2d327..5ad808a25a 100644
> --- a/accel/tcg/user-exec.c
> +++ b/accel/tcg/user-exec.c
> @@ -28,6 +28,7 @@
>  #include "qemu/atomic128.h"
>  #include "trace/trace-root.h"
>  #include "trace/mem.h"
> +#include "internal.h"
>  
>  #undef EAX
>  #undef ECX
> @@ -1230,11 +1231,22 @@ static void *atomic_mmu_lookup(CPUArchState *env, 
> target_ulong addr,
>                                 TCGMemOpIdx oi, int size, int prot,
>                                 uintptr_t retaddr)
>  {
> +    MemOp mop = get_memop(oi);
> +    int a_bits = get_alignment_bits(mop);
> +    void *ret;
> +
> +    /* Enforce guest required alignment.  */
> +    if (unlikely(addr & ((1 << a_bits) - 1))) {
> +        MMUAccessType t = prot == PAGE_READ ? MMU_DATA_LOAD : MMU_DATA_STORE;
> +        cpu_unaligned_access(env_cpu(env), addr, t, get_mmuidx(oi), retaddr);
> +    }
> +
>      /* Enforce qemu required alignment.  */
>      if (unlikely(addr & (size - 1))) {
>          cpu_loop_exit_atomic(env_cpu(env), retaddr);
>      }
> -    void *ret = g2h(env_cpu(env), addr);
> +
> +    ret = g2h(env_cpu(env), addr);
>      set_helper_retaddr(retaddr);
>      return ret;

Can't we simply do:

       return g2h(env_cpu(env), addr);

?

>  }
>