Re: of AVR target page size

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

* Michael Rolnik (mrolnik@gmail.com) wrote:
> how do I test my fix? Is there a procedure?

As long as your TARGET_PAGE_SIZE is now 512 or bigger you should be OK
as long as your AVR stuff still works.  If you want you can try and do a
live migrate between two copies of qemu, but that does assume you'vre
wired up the vmstate info for all your devices.

Dave

> Thanks,
> Michael Rolnik
> 
> On Thu, Mar 18, 2021 at 12:45 PM Dr. David Alan Gilbert <dgilbert@redhat.com>
> wrote:
> 
> > * 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
> >
> >
> 
> -- 
> Best Regards,
> Michael Rolnik
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK