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

Aneesh Kumar K.V aneesh.kumar at linux.vnet.ibm.com
Fri Jan 31 22:28:05 EST 2014

Paul Mackerras <paulus at samba.org> writes:

> 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
> 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 ?


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