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

Jiri Slaby
2013-03-01T09:22:31Z

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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,
--
js
suse labs

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From: Jiri Slaby <jslaby@suse.cz>
Subject: s390/kvm: Fix store status for ACRS/FPRS fix
Patch-mainline: no, submitted on 1st Mar 2013

In 3.0.67, commit 58c9ce6fad8e00d9726447f939fe7e78e2aec891 (s390/kvm:
Fix store status for ACRS/FPRS), upstream commit
15bc8d8457875f495c59d933b05770ba88d1eacb, added a call to
save_access_regs to save ACRS. But we do not have ARCS in kvm_run in
3.0 yet, so this results in:
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'

Fix it by saving guest_acrs which is where ARCS are in 3.0.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
arch/s390/kvm/kvm-s390.c | 1 -
1 file changed, 1 deletion(-)

--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -590,7 +590,7 @@ int kvm_s390_vcpu_store_status(struct kv
* it into the save area
*/
save_fp_regs(&vcpu->arch.guest_fpregs);
- save_access_regs(vcpu->run->s.regs.acrs);
+ save_access_regs(vcpu->arch.guest_acrs);

if (__guestcopy(vcpu, addr + offsetof(struct save_area, fp_regs),
vcpu->arch.guest_fpregs.fprs, 128, prefix))