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

[Segher Boessenkool]

> +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 :-)

> +	__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