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

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Date:	Thu, 28 Feb 2013 23:26:59 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
CC:	stable@...r.kernel.org,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Gleb Natapov <gleb@...hat.com>
Subject: Re: [ 17/53] s390/kvm: Fix store status for ACRS/FPRS

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?

thanks,
-- 
js
suse labs
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