Re: [PATCH] qemu/timer: Don't use RDTSC on i486

[Petr Cvek]

Dne 26. 11. 23 v 16:56 Paolo Bonzini napsal(a):
> 
> 
> Il sab 25 nov 2023, 13:23 Petr Cvek <petrcvekcz@gmail.com 
> <mailto:petrcvekcz@gmail.com>> ha scritto:
> 
>     GCC defines __i386__ for i386 and i486, which both lack RDTSC instruction.
>     The i386 seems to be impossible to distinguish, but i486 can be identified
>     by checking for undefined __i486__.
> 
> 
> As far as I know QEMU cannot be run on i486 anyway since TCG assumes the 
> presence of CPUID. Have you actually tried?
> 

Yes I tried running x86_64 mesa3d glxgears on amd 5x86. It worked with about 5 
fps :). Latest 486 CPUs supports CPUID btw.

> Paolo
> 
> 
>     Signed-off-by: Petr Cvek <petrcvekcz@gmail.com 
> <mailto:petrcvekcz@gmail.com>>
>     ---
>      include/qemu/timer.h | 2 +-
>      1 file changed, 1 insertion(+), 1 deletion(-)
> 
>     diff --git a/include/qemu/timer.h b/include/qemu/timer.h
>     index 9a366e551f..7baa5d1d41 100644
>     --- a/include/qemu/timer.h
>     +++ b/include/qemu/timer.h
>     @@ -872,7 +872,7 @@ static inline int64_t cpu_get_host_ticks(void)
>          return retval;
>      }
> 
>     -#elif defined(__i386__)
>     +#elif defined(__i386__) && !defined(__i486__)
> 
>      static inline int64_t cpu_get_host_ticks(void)
>      {
>     -- 
>     2.43.0
>