Re: [Xen-devel] [PATCH] Avoid cpu_physical_memory_rw() with a constant is_write argument

[Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>]

On 2/18/20 7:49 PM, Peter Maydell wrote:
> On Tue, 18 Feb 2020 at 17:57, Stefan Weil <sw@xxxxxxxxxxx> wrote:
> > Am 18.02.20 um 14:20 schrieb Philippe Mathieu-Daudé:
> >
> > > This commit was produced with the included Coccinelle script
> > > scripts/coccinelle/as-rw-const.patch.
> > >
> > > Inspired-by: Peter Maydell <peter.maydell@xxxxxxxxxx>
> > > Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
> > > ---
> > > Based-on: <20200218112457.22712-1-peter.maydell@xxxxxxxxxx>
> > [...]
> > > diff --git a/target/i386/hax-all.c b/target/i386/hax-all.c
> > > index a8b6e5aeb8..f5971ccc74 100644
> > > --- a/target/i386/hax-all.c
> > > +++ b/target/i386/hax-all.c
> > > @@ -376,8 +376,8 @@ static int hax_handle_fastmmio(CPUArchState *env, struct 
> > > hax_fastmmio *hft)
> > >            *  hft->direction == 2: gpa ==> gpa2
> > >            */
> > >           uint64_t value;
> > > -        cpu_physical_memory_rw(hft->gpa, (uint8_t *) &value, hft->size, 0);
> > > -        cpu_physical_memory_rw(hft->gpa2, (uint8_t *) &value, hft->size, 1);
> > > +        cpu_physical_memory_read(hft->gpa, (uint8_t *)&value, hft->size);
> > > +        cpu_physical_memory_write(hft->gpa2, (uint8_t *)&value, hft->size);
> >
> > Maybe those type casts could be removed, too. They are no longer needed
> > after your modification.
> I think that we should fix the inconsistency where these functions
> all take "uint8_t* buf":
>
>   - address_space_rw()
>   - address_space_read()
>   - address_space_write()
>   - address_space_write_rom()
>   - cpu_physical_memory_rw()
>   - cpu_memory_rw_debug()
>
> but these take void*:
>   - cpu_physical_memory_read()
>   - cpu_physical_memory_write()
>   - address_space_write_cached()
>   - address_space_read_cached_slow()
>   - address_space_write_cached_slow()
>   - pci_dma_read()
>   - pci_dma_write()
>   - pci_dma_rw()
>   - dma_memory_read()
>   - dma_memory_write()
>   - dma_memory_rw()
>   - dma_memory_rw_relaxed()
I don't understand well cpu_physical_memory*(). Aren't these obsolete?
They confuse me when using multi-core CPUs.

> Depending on which way we go we would either want to remove these
> casts, or not.
>
> I guess that we have more cases of 'void*', and that would
> certainly be the easier way to convert (otherwise we probably
> need to add a bunch of new casts to uint8_t* in various callsites),
> but I don't have a strong opinion. Paolo ?
I thought about it too but it is quite some work, and I'v to admit I 
lost some faith with my previous chardev conversion. There Paolo/Daniel 
agreed to follow the libc read()/write() prototypes.
> thanks
> -- PMM

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