Re: [PATCH v2 8/8] kvm tools: Use brlock in MMIO and IOPORT

[Sasha Levin <levinsasha928@gmail.com>]

On Mon, 2011-05-30 at 10:47 +0200, Ingo Molnar wrote:
> * Sasha Levin <levinsasha928@gmail.com> wrote:
> 
> > @@ -55,41 +56,53 @@ static const char *to_direction(u8 is_write)
> >  bool kvm__register_mmio(u64 phys_addr, u64 phys_addr_len, void (*kvm_mmio_callback_fn)(u64 addr, u8 *data, u32 len, u8 is_write))
> >  {
> >  	struct mmio_mapping *mmio;
> > +	int ret;
> >  
> >  	mmio = malloc(sizeof(*mmio));
> >  	if (mmio == NULL)
> >  		return false;
> >  
> > +	br_write_lock();
> >  	*mmio = (struct mmio_mapping) {
> >  		.node = RB_INT_INIT(phys_addr, phys_addr + phys_addr_len),
> >  		.kvm_mmio_callback_fn = kvm_mmio_callback_fn,
> >  	};
> 
> The initialization here does not use any global state AFAICS so it 
> does not need the write lock, right?
> 
> >  
> > -	return mmio_insert(&mmio_tree, mmio);
> > +	ret = mmio_insert(&mmio_tree, mmio);
> > +	br_write_unlock();
> 
> Shouldnt mmio_insert() thus have the write_lock()/unlock() sequence?

Yes, the lock can be reduced to just the insert.

> >  bool kvm__deregister_mmio(u64 phys_addr)
> >  {
> >  	struct mmio_mapping *mmio;
> >  
> > +	br_write_lock();
> >  	mmio = mmio_search_single(&mmio_tree, phys_addr);
> >  	if (mmio == NULL)
> >  		return false;
> 
> Here we leak the write lock!
> 
> >  bool kvm__emulate_mmio(struct kvm *kvm, u64 phys_addr, u8 *data, u32 len, u8 is_write)
> >  {
> > -	struct mmio_mapping *mmio = mmio_search(&mmio_tree, phys_addr, len);
> > +	struct mmio_mapping *mmio;
> > +
> > +	br_read_lock();
> > +	mmio = mmio_search(&mmio_tree, phys_addr, len);
> >  
> >  	if (mmio)
> >  		mmio->kvm_mmio_callback_fn(phys_addr, data, len, is_write);
> >  	else
> >  		fprintf(stderr, "Warning: Ignoring MMIO %s at %016llx (length %u)\n",
> >  			to_direction(is_write), phys_addr, len);
> > +	br_read_unlock();
> >  
> >  	return true;
> >  }
> 
> Yummie, scalability here we come! :-)
> 
> Thanks,
> 
> 	Ingo

-- 

Sasha.