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Date: Thu, 30 Jan 2014 17:00:00 +1100
From: Paul Mackerras <paulus@samba.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 07/10] KVM: PPC: BOOK3S: PR: Emulate facility status
 and control register
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On Tue, Jan 28, 2014 at 10:14:12PM +0530, Aneesh Kumar K.V wrote:
> We allow priv-mode update of this. The guest value is saved in fscr,
> and the value actually used is saved in shadow_fscr. shadow_fscr
> only contains values that are allowed by the host. On
> facility unavailable interrupt, if the facility is allowed by fscr
> but disabled in shadow_fscr we need to emulate the support. Currently
> all but EBB is disabled. We still don't support performance monitoring
> in PR guest.

...

> +	/*
> +	 * Save the current fscr in shadow fscr
> +	 */
> +	mfspr r3,SPRN_FSCR
> +	PPC_STL r3, VCPU_SHADOW_FSCR(r7)

I don't think you need to do this.  What could possibly have changed
FSCR since we loaded it on the way into the guest?

Paul.