Re: [PATCH 14/15] KVM: PPC: Add OSI hypercall interface

[Avi Kivity <avi@redhat.com>]

On 03/08/2010 08:03 PM, Alexander Graf wrote:
> MOL uses its own hypercall interface to call back into userspace when
> the guest wants to do something.
>
> So let's implement that as an exit reason, specify it with a CAP and
> only really use it when userspace wants us to.
>
> The only user of it so far is MOL.
>
> Signed-off-by: Alexander Graf<agraf@suse.de>
>
> ---
>
> v1 ->  v2:
>
>    - Add documentation for OSI exit struct
> ---
>   Documentation/kvm/api.txt             |   13 +++++++++++++
>   arch/powerpc/include/asm/kvm_book3s.h |    5 +++++
>   arch/powerpc/include/asm/kvm_host.h   |    2 ++
>   arch/powerpc/kvm/book3s.c             |   24 ++++++++++++++++++------
>   arch/powerpc/kvm/powerpc.c            |   12 ++++++++++++
>   include/linux/kvm.h                   |    6 ++++++
>   6 files changed, 56 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
> index 6a19ab6..b2129e8 100644
> --- a/Documentation/kvm/api.txt
> +++ b/Documentation/kvm/api.txt
> @@ -932,6 +932,19 @@ s390 specific.
>
>   powerpc specific.
>
> +		/* KVM_EXIT_OSI */
> +		struct {
> +			__u64 gprs[32];
> +		} osi;
> +
> +MOL uses a special hypercall interface it calls 'OSI'. To enable it, we catch
> +hypercalls and exit with this exit struct that contains all the guest gprs.
> +
> +If exit_reason is KVM_EXIT_OSI, then the vcpu has triggered such a hypercall.
> +Userspace can now handle the hypercall and when it's done modify the gprs as
> +necessary. Upon guest entry all guest GPRs will then be replaced by the values
> +in this struct.
> +
>    

That's migration unsafe.  There may not be next guest entry on this host.

Is using KVM_[GS]ET_REGS problematic for some reason?

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