Re: [PATCH v3] tcg: Fix execution on Apple Silicon

[Roman Bolshakov]

On Fri, Jan 29, 2021 at 10:18:58AM -1000, Richard Henderson wrote:
> On 1/21/21 8:34 AM, Richard Henderson wrote:
> > On 1/12/21 5:28 PM, Roman Bolshakov wrote:
> >> @@ -1083,6 +1083,12 @@ static bool alloc_code_gen_buffer_anon(size_t size, 
> >> int prot,
> >>  {
> >>      void *buf;
> >>  
> >> +#if defined(MAC_OS_VERSION_11_0) && \
> >> +    MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_VERSION_11_0
> >> +    if (__builtin_available(macOS 11.0, *)) {
> >> +        flags |= MAP_JIT;
> >> +    }
> >> +#endif
> > 
> > This hunk should be in alloc_code_gen_buffer, where we do the other flags
> > manipulation.
> > 
> > I'll drop this hunk and apply the rest, which is exclusively related to
> > toggling the jit bit.
> 
> Ping on this?
> 
Hi Richard,

> I would imagine that the patch would look something like
> 
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -1296,6 +1296,11 @@ static bool alloc_code_gen_buffer
>  #ifdef CONFIG_TCG_INTERPRETER
>      /* The tcg interpreter does not need execute permission. */
>      prot = PROT_READ | PROT_WRITE;
> +#elif defined(MAC_OS_VERSION_11_0) && \
> +    MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_VERSION_11_0
> +    if (__builtin_available(macOS 11.0, *)) {
> +        flags |= MAP_JIT;
> +    }
>  #elif defined(CONFIG_DARWIN)
>      /* Applicable to both iOS and macOS (Apple Silicon). */
>      if (!splitwx) {
> 
> But I don't know how CONFIG_DARWIN, iOS, and MAC_OS_VERSION interact, and I'm
> not able to even compile-test the patch.
> Certainly the final comment there looks suspicious, given the preceding MAC_OS
> stanza...
> 

I thought you already added MAP_JIT in 6f70ddee19e. It's getting enabled
on my M1 laptop. Was it intended or not?

    /* Applicable to both iOS and macOS (Apple Silicon). */
    if (!splitwx) {
        flags |= MAP_JIT;
    }

TCG from master branch of QEMU works fine on M1. I'm not sure why do we
need to duplicate it.

Thanks,
Roman