Re: [PATCH 1/4] kvm-s390: add capability indicating COW support

[Avi Kivity <avi@redhat.com>]

On 05/15/2012 03:15 PM, Christian Borntraeger wrote:
> Currently qemu/kvm on s390 uses a guest mapping that does not
> allow the guest backing page table to be write-protected to
> support older systems. On those older systems a host write
> protection fault will be delivered to the guest.
>
> Newer systems allow to write-protect the guest backing memory
> and let the fault be delivered to the host, thus allowing COW.
>
> Use a capability bit to tell qemu if that is possible.
>

Asking out of ignorance: who is doing the write protection here? The
guest?  If so, why is qemu involved?

Or is qemu just passing the capability on to the guest?

btw, we usually use 'userspace' in kernel patches instead of qemu to
create the illusion that it's not the only consumer of kvm interfaces.

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