Re: [ 17/53] s390/kvm: Fix store status for ACRS/FPRS

Greg Kroah-Hartman
2013-03-01T19:16:59Z

On Fri, Mar 01, 2013 at 10:22:23AM +0100, Jiri Slaby wrote:
> On 03/01/2013 08:50 AM, Christian Borntraeger wrote:
> > On 28/02/13 23:26, Jiri Slaby wrote:
> >> On 02/27/2013 12:57 AM, Greg Kroah-Hartman wrote:
> >>> 3.0-stable review patch. If anyone has any objections, please let me know.
> >>>
> >>> ------------------
> >>>
> >>> From: Christian Borntraeger <borntraeger@de.ibm.com>
> >>>
> >>> commit 15bc8d8457875f495c59d933b05770ba88d1eacb upstream.
> >>>
> >>> On store status we need to copy the current state of registers
> >>> into a save area. Currently we might save stale versions:
> >>> The sie state descriptor doesnt have fields for guest ACRS,FPRS,
> >>> those registers are simply stored in the host registers. The host
> >>> program must copy these away if needed. We do that in vcpu_put/load.
> >>>
> >>> If we now do a store status in KVM code between vcpu_put/load, the
> >>> saved values are not up-to-date. Lets collect the ACRS/FPRS before
> >>> saving them.
> >>>
> >>> This also fixes some strange problems with hotplug and virtio-ccw,
> >>> since the low level machine check handler (on hotplug a machine check
> >>> will happen) will revalidate all registers with the content of the
> >>> save area.
> >>>
> >>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> >>> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> >>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >>>
> >>> ---
> >>> arch/s390/kvm/kvm-s390.c | 8 ++++++++
> >>> 1 file changed, 8 insertions(+)
> >>>
> >>> --- a/arch/s390/kvm/kvm-s390.c
> >>> +++ b/arch/s390/kvm/kvm-s390.c
> >>> @@ -584,6 +584,14 @@ int kvm_s390_vcpu_store_status(struct kv
> >>> } else
> >>> prefix = 0;
> >>>
> >>> + /*
> >>> + * The guest FPRS and ACRS are in the host FPRS/ACRS due to the lazy
> >>> + * copying in vcpu load/put. Lets update our copies before we save
> >>> + * it into the save area
> >>> + */
> >>> + save_fp_regs(&vcpu->arch.guest_fpregs);
> >>> + save_access_regs(vcpu->run->s.regs.acrs);
> >>
> >> kvm_run structure does not have kvm_sync_regs in it in 3.0 yet. So this
> >> fails with:
> >> arch/s390/kvm/kvm-s390.c: In function 'kvm_s390_vcpu_store_status':
> >> arch/s390/kvm/kvm-s390.c:593: error: 'struct kvm_run' has no member
> >> named 's'
> >>
> >> I believe the fix is just to remove save_access_regs, right?
> >
> > Before the sync reg changes, the ACRS were saved in the vcpu->arch.
> > So the fix would look like
> >
> > save_access_regs(vcpu->arch.guest_acrs);
>
> Fix attached.

Thanks, now applied.

greg k-h