Re: [Qemu-devel] [PATCH 2/2] migration: Poison ramblock loops in migration

[Dr. David Alan Gilbert]

* Peter Xu (address@hidden) wrote:
> On Wed, Jun 06, 2018 at 11:36:00AM +0800, Peter Xu wrote:
> > On Tue, Jun 05, 2018 at 05:25:45PM +0100, Dr. David Alan Gilbert (git) 
> > wrote:
> > > From: "Dr. David Alan Gilbert" <address@hidden>
> > > 
> > > The migration code should be using the
> > >   RAMBLOCK_FOREACH_MIGRATABLE and qemu_ram_foreach_block_migratable
> > > not the all-block versions;  poison them so that we can't accidentally
> > > use them.
> > > 
> > > Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> > > ---
> > >  include/exec/ramlist.h | 4 +++-
> > >  migration/migration.h  | 3 +++
> > >  migration/ram.c        | 4 +++-
> > >  3 files changed, 9 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/include/exec/ramlist.h b/include/exec/ramlist.h
> > > index 2e2ac6cb99..bc4faa1b00 100644
> > > --- a/include/exec/ramlist.h
> > > +++ b/include/exec/ramlist.h
> > > @@ -56,8 +56,10 @@ typedef struct RAMList {
> > >  extern RAMList ram_list;
> > >  
> > >  /* Should be holding either ram_list.mutex, or the RCU lock. */
> > > -#define  RAMBLOCK_FOREACH(block)  \
> > > +#define  INTERNAL_RAMBLOCK_FOREACH(block)  \
> > >      QLIST_FOREACH_RCU(block, &ram_list.blocks, next)
> > > +/* Never use the INTERNAL_ version except for defining other macros */
> > > +#define RAMBLOCK_FOREACH(block) INTERNAL_RAMBLOCK_FOREACH(block)
> > >  
> > >  void qemu_mutex_lock_ramlist(void);
> > >  void qemu_mutex_unlock_ramlist(void);
> > > diff --git a/migration/migration.h b/migration/migration.h
> > > index 5af57d616c..31d3ed12dc 100644
> > > --- a/migration/migration.h
> > > +++ b/migration/migration.h
> > > @@ -284,4 +284,7 @@ void 
> > > migrate_send_rp_resume_ack(MigrationIncomingState *mis, uint32_t value);
> > >  void dirty_bitmap_mig_before_vm_start(void);
> > >  void init_dirty_bitmap_incoming_migration(void);
> > >  
> > > +#define qemu_ram_foreach_block \
> > > +  #warning "Use qemu_ram_foreach_block_migratable in migration code"
> > > +
> > >  #endif
> > > diff --git a/migration/ram.c b/migration/ram.c
> > > index a7807cea84..e0d19305ee 100644
> > > --- a/migration/ram.c
> > > +++ b/migration/ram.c
> > > @@ -159,9 +159,11 @@ out:
> > >  
> > >  /* Should be holding either ram_list.mutex, or the RCU lock. */
> > >  #define RAMBLOCK_FOREACH_MIGRATABLE(block)             \
> > > -    RAMBLOCK_FOREACH(block)                            \
> > > +    INTERNAL_RAMBLOCK_FOREACH(block)                   \
> > >          if (!qemu_ram_is_migratable(block)) {} else
> > >  
> > > +#undef RAMBLOCK_FOREACH
> > 
> > This will only cover the ram.c file.  How about we move
> > RAMBLOCK_FOREACH_MIGRATABLE() directly into migration.h then undef
> > RAMBLOCK_FOREACH there?  Then since migration.h should be used in all
> > the migration internal source files so the poisoned bit can be used in
> > a broader aspect?
> 
> (I forgot to reply-all.... forwarding to the list)

Yes, we could; although it's only the ram.c that's compiled
target specific and can include the header that allows use of those macros 
anyway.

Dave

> > 
> > Thanks,
> > 
> > > +
> > >  static void ramblock_recv_map_init(void)
> > >  {
> > >      RAMBlock *rb;
> > > -- 
> > > 2.17.0
> > > 
> > 
> > -- 
> > Peter Xu
> 
> -- 
> Peter Xu
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK