Re: [RFC] need to improve slot creation/destruction? -- Re: [RFC][PATCH] srcu: Implement call_srcu()

[Avi Kivity <avi@redhat.com>]

On 02/10/2012 03:25 PM, Takuya Yoshikawa wrote:
> Avi Kivity <avi@redhat.com> wrote:
>
> > > 2. When we create(and shift?) a memory slot, we call kvm_arch_flush_shadow()
> > > to clear all mmio sptes, again not restricted to that slot.
> > >
> > > 	/*
> > > 	 * If the new memory slot is created, we need to clear all
> > > 	 * mmio sptes.
> > > 	 */
> > > 	if (npages && old.base_gfn != mem->guest_phys_addr >> PAGE_SHIFT)
> > > 		kvm_arch_flush_shadow(kvm);
> > 
> > This is pretty rare outside the previous scenario (memory/pci hotplug).
>
> Is this condition correct?
>
> When npages != 0 and old.npages == 0, the slot is being newly created, do we
> really need to flush shadow pages?
>
> This should be
> 	if (npages && old.npages && (old.base_gfn != base_gfn))
>

Your condition is more correct, but in practice there's no difference. 
If old.npages == 0, then old.base_gfn will be 0, and the condition will
fail, except for the first slot created (when the shadow cache is empty
anyway).

-- 
error compiling committee.c: too many arguments to function