Re: of AVR target page size

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Maydell (peter.maydell@linaro.org) wrote:
> On Thu, 18 Mar 2021 at 10:25, Dr. David Alan Gilbert
> <dgilbert@redhat.com> wrote:
> > Oh yes, just:
> >
> > diff --git a/migration/ram.c b/migration/ram.c
> > index 52537f14ac..a7269955b5 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -81,6 +81,8 @@
> >  /* 0x80 is reserved in migration.h start with 0x100 next */
> >  #define RAM_SAVE_FLAG_COMPRESS_PAGE    0x100
> >
> > +#define RAM_SAVE_FLAG__MAX RAM_SAVE_FLAG_COMPRESS_PAGE
> > +
> >  static inline bool is_zero_range(uint8_t *p, uint64_t size)
> >  {
> >      return buffer_is_zero(p, size);
> > @@ -4090,5 +4092,6 @@ static SaveVMHandlers savevm_ram_handlers = {
> >  void ram_mig_init(void)
> >  {
> >      qemu_mutex_init(&XBZRLE.lock);
> > +    QEMU_BUILD_BUG_ON(RAM_SAVE_FLAG__MAX >= (1 << TARGET_PAGE_BITS_MIN));
> >      register_savevm_live("ram", 0, 4, &savevm_ram_handlers, &ram_state);
> >  }
> >
> >
> > works; lets keep that in mind somewhere after Michael fixes AVR.
> 
> You don't have a great deal of headroom even after getting AVR
> to change, by the way -- TARGET_PAGE_BITS_MIN for Arm is 10.
> So you might want to think about ways to eg reclaim usage of
> that "obsolete, not used" RAM_SAVE_FLAG_FULL bit.

Yep, I've been warning anyone who adds one for ages

> Also, what does the
>  /* 0x80 is reserved in migration.h start with 0x100 next */
> comment refer to? migration.h has no instances of "RAM_SAVE"
> or 0x80 or 1 << 7...

It looks like it got moved to qemu-file.h a few years ago
as RAM_SAVE_FLAG_HOOK.

Dave

> thanks
> -- PMM
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK