Re: [kvm-devel] [PATCH 0 of 9] mmu notifier #v12

[Andrea A. <an...@qu...>]

On Tue, Apr 22, 2008 at 08:01:20AM -0500, Robin Holt wrote:
> On Tue, Apr 22, 2008 at 02:00:56PM +0200, Andrea Arcangeli wrote:
> > On Tue, Apr 22, 2008 at 09:20:26AM +0200, Andrea Arcangeli wrote:
> > >     invalidate_range_start {
> > > 	spin_lock(&kvm->mmu_lock);
> > > 
> > > 	kvm->invalidate_range_count++;
> > > 	rmap-invalidate of sptes in range
> > > 
> > 
> > 	write_seqlock; write_sequnlock;
> 
> I don't think you need it here since invalidate_range_count is already
> elevated which will accomplish the same effect.

Agreed, seqlock only in range_end should be enough. BTW, the fact
seqlock is needed regardless of invalidate_page existing or not,
really makes invalidate_page a no brainer not just from the core VM
point of view, but from the driver point of view too. The
kvm_page_fault logic would be the same even if I remove
invalidate_page from the mmu notifier patch but it'd run slower both
when armed and disarmed.