Subject: Re: [PATCH 27/27] KVM: PPC: Add Documentation about PV interface

From: Benjamin Herrenschmidt <[email-masked]>
Date: Sun, 04 Jul 2010 08:41:49 +1000

On Fri, 2010-07-02 at 18:27 +0200, Segher Boessenkool wrote:
> > +To find out if we're running on KVM or not, we overlay the PVR  
> > register. Usually
> > +the PVR register contains an id that identifies your CPU type. If,  
> > however, you
> > +pass KVM_PVR_PARA in the register that you want the PVR result in,  
> > the register
> > +still contains KVM_PVR_PARA after the mfpvr call.
> > +
> > +	LOAD_REG_IMM(r5, KVM_PVR_PARA)
> > +	mfpvr	r5
> > +	[r5 still contains KVM_PVR_PARA]
> 
> I love this part :-)

Me not :-)

It should be in the device-tree instead, or something like that. Enough
games with PVR...

Ben.

> > +	__u64 scratch3;
> > +	__u64 critical;		/* Guest may not get interrupts if == r1 */
> > +	__u64 sprg0;
> > +	__u64 sprg1;
> > +	__u64 sprg2;
> > +	__u64 sprg3;
> > +	__u64 srr0;
> > +	__u64 srr1;
> > +	__u64 dar;
> > +	__u64 msr;
> > +	__u32 dsisr;
> > +	__u32 int_pending;	/* Tells the guest if we have an interrupt */
> > +};
> > +
> > +Additions to the page must only occur at the end. Struct fields  
> > are always 32
> > +bit aligned.
> 
> The u64s are 64-bit aligned, should they always be?
> 
> > +The "ld" and "std" instructions are transormed to "lwz" and "stw"  
> > instructions
> > +respectively on 32 bit systems with an added offset of 4 to  
> > accomodate for big
> > +endianness.
> 
> Will this add never overflow?  Is there anything that checks for it?
> 
> > +mtmsrd	rX, 0		b	<special mtmsr section>
> > +mtmsr			b	<special mtmsr section>
> 
> mtmsr rX
> 
> 
> Segher
> 
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