[Gcl-devel] Re: m68k cacheflushing

[Richard Zidlicky]

On Fri, Nov 22, 2002 at 10:50:56PM -0500, Camm Maguire wrote:

cc'd to linux-m68k where kernel question should go

> Greetings! gcl/acl2 loads many modules into its data section,
> relocates, flushes the cache, and then executes the module.
> The CACHE_LINE granularity option to cacheflush appears to be broken,
> at least on 060. 

gcc and glibc use the same already for ages and never had any 
problems it appears.

> The following two have been tested and fail, whereas
> the third has been tested and passes:
> 
> 
> #define CLEAR_CACHE_LINE_SIZE 32
> #define CLEAR_CACHE do {void 
> *v=memory->cfd.cfd_start,*ve=v+memory->cfd.cfd_size; \
>                         cacheflush(v,FLUSH_SCOPE_LINE,FLUSH_CACHE_BOTH,ve-v);\
>                     } while(0)
> 
> #define CLEAR_CACHE_LINE_SIZE 32
> #define CLEAR_CACHE do {void 
> *v=memory->cfd.cfd_start,*ve=v+memory->cfd.cfd_size; \
>                         v=(void *)((unsigned long)v & ~(CLEAR_CACHE_LINE_SIZE 
> - 1));\
>                         cacheflush(v,FLUSH_SCOPE_LINE,FLUSH_CACHE_BOTH,ve-v);\
>                     } while(0)
> 
> #define CLEAR_CACHE_LINE_SIZE 32
> #define CLEAR_CACHE do {void 
> *v=memory->cfd.cfd_start,*ve=v+memory->cfd.cfd_size; \
>                         v=(void *)((unsigned long)v & ~(CLEAR_CACHE_LINE_SIZE 
> - 1));\
>                         cacheflush(v,FLUSH_SCOPE_PAGE,FLUSH_CACHE_BOTH,ve-v);\
>                     } while(0)
> 
> 
> I haven't tried the remaining cache-line case of rounding ve up to the
> nearest 32 byte boundary, but barring this, there appears to be an error
> in the cacheflush kernel function.

aligning/rounding the address should not be necessary anyway. 
cacheflush returns 0 on success or -1 and errno so for debugging it 
would be very good idea to test for errors. The complete range passed 
to cacheflush must be legal address, otherwise cacheflush will return 
an error without doing any flush. 

Which kernel version was that? Can you see if the failed flushes
were cornercases like address near page-boundaries? What kind
of ranges need to be flushed?

Richard