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

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Date:	Fri, 01 Mar 2013 08:50:29 +0100
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Jiri Slaby <jslaby@...e.cz>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Gleb Natapov <gleb@...hat.com>
Subject: Re: [ 17/53] s390/kvm: Fix store status for ACRS/FPRS

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@...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@...ibm.com>
>> Signed-off-by: Gleb Natapov <gleb@...hat.com>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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);


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