Re: [PATCH v2 1/4] util/cacheflush: fix cache on windows-arm64

[Pierrick Bouvier]

On 2/16/23 20:42, Richard Henderson wrote:
> On 2/16/23 03:49, Pierrick Bouvier wrote:
> > ctr_el0 access is privileged on this platform and fails as an illegal
> > instruction.
> >
> > Windows does not offer a way to flush data cache from userspace, and
> > only FlushInstructionCache is available in Windows API.
> >
> > The generic implementation of flush_idcache_range uses,
> > __builtin___clear_cache, which already use the FlushInstructionCache
> > function. So we rely on that.
> >
> > Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
>
> This is reasonable for now.  I'll note that gcc does not yet support windows 
> for aarch64,
> and I would guess this would be fixed for libgcc at such time as.
>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

For completeness, and after asking to Microsoft,
FlushInstructionCache does DCache-Clean-to-PoU + 
ICache-Invalidate-to-PoU, which is equivalent to calling dccvau + icivau.

Thus, it's doing the right thing.

Pierrick

> r~
>
>
> > ---
> >    util/cacheflush.c | 10 +++++++---
> >    1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/util/cacheflush.c b/util/cacheflush.c
> > index 2c2c73e085..0a0acd70fa 100644
> > --- a/util/cacheflush.c
> > +++ b/util/cacheflush.c
> > @@ -121,8 +121,10 @@ static void sys_cache_info(int *isize, int *dsize)
> >    static bool have_coherent_icache;
> >    #endif
> >    
> > -#if defined(__aarch64__) && !defined(CONFIG_DARWIN)
> > -/* Apple does not expose CTR_EL0, so we must use system interfaces. */
> > +#if defined(__aarch64__) && !defined(CONFIG_DARWIN) && !defined(CONFIG_WIN32)
> > +/* Apple does not expose CTR_EL0, so we must use system interfaces.
> > + * Windows neither, but we use a generic implementation of flush_idcache_range
> > + * in this case. */
> >    static uint64_t save_ctr_el0;
> >    static void arch_cache_info(int *isize, int *dsize)
> >    {
> > @@ -225,7 +227,9 @@ static void __attribute__((constructor)) 
> > init_cache_info(void)
> >    
> >    /* Caches are coherent and do not require flushing; symbol inline. */
> >    
> > -#elif defined(__aarch64__)
> > +#elif defined(__aarch64__) && !defined(CONFIG_WIN32)
> > +/* For Windows, we use generic implementation of flush_idcache_range, that
> > + * performs a call to FlushInstructionCache, through __builtin___clear_cache */
> >    
> >    #ifdef CONFIG_DARWIN
> >    /* Apple does not expose CTR_EL0, so we must use system interfaces. */