Re: KVM: MMU: add KVM_ZAP_GFN ioctl

Andrea Arcangeli
2008-03-21T11:42:14Z

On Thu, Mar 20, 2008 at 02:09:15PM +0200, Avi Kivity wrote:
> Marcelo Tosatti wrote:
> > Add an ioctl to zap all mappings to a given gfn. This allows userspace
> > remove the QEMU process mappings and the page without causing
> > inconsistency.
> >
> >
>
> I'm thinking of comitting rmap_nuke() to kvm.git, and the rest to the
> external module, since this is only needed on kernels without mmu notifiers.
>
> Andrea, is rmap_nuke() suitable for the mmu notifiers pte clear callback?

There's the usual smp race condition. The tlb must be flushed before
the final put_page in rmap_remove. And it can't be safe to call this
ioctl before sys_munmap(), so this would be the final put_page.

My kvm_unmap_hva takes care of that.