Re: [RFC PATCH 07/10] KVM: PPC: BOOK3S: PR: Emulate facility status and control register

Paul Mackerras [off-list ref] writes:

On Tue, Jan 28, 2014 at 10:14:12PM +0530, Aneesh Kumar K.V wrote:

quoted

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.

...

quoted

+	/*
+	 * 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?

The reason for facility unavailable interrupt is encoded in FSCR right ?

-aneesh