RE: [patch 0/4] add e500 platform support for KVM

[Hollis Blanchard <hollisb@us.ibm.com>]

On Thu, 2008-09-11 at 16:43 +0800, Liu Yu-B13201 wrote:
> > 
> > Could you talk a little about how it differs from the 440
> > implementation? For example, how are you using TLB0 and TLB1?
> > 
> > Some of the refactoring you've done, like creating completely separate
> > kvmppc_handle_tlb_miss() functions, surprises me. For example, I'd
> > expect the DTLB miss code to be refactored like this:
> > 
> >         case BOOKE_INTERRUPT_DTLB_MISS:	
> >         	gtlbe = kvmppc_dtlb_search(vcpu, eaddr); <- CORE HOOK
> >         	if (!gtlbe) {
> >         		/* The guest didn't have a mapping for it. */
> >         		kvmppc_queue_exception(vcpu, exit_nr);
> >         		vcpu->arch.dear = vcpu->arch.fault_dear;
> >         		vcpu->arch.esr = vcpu->arch.fault_esr;
> >         		kvmppc_deliver_dtlb_miss(vcpu); <- CORE HOOK
> >         		vcpu->stat.dtlb_real_miss_exits++;
> >         		r = RESUME_GUEST;
> >         		break;
> >         	}
> >         
> >         	vcpu->arch.paddr_accessed = tlb_xlate(gtlbe, eaddr);
> >         	gfn = vcpu->arch.paddr_accessed >> PAGE_SHIFT;
> >         
> >         	if (kvm_is_visible_gfn(vcpu->kvm, gfn)) {
> >         		kvmppc_mmu_map(vcpu, eaddr, gfn, gtlbe->tid,
> >         		               gtlbe->word2); <- CORE HOOK
> >         		vcpu->stat.dtlb_virt_miss_exits++;
> >         		r = RESUME_GUEST;
> >         	} else
> >         		r = kvmppc_emulate_mmio(run, vcpu);
> >         
> >         	break;
> > 
> 
> Hollis, I'm reconsiderring this place.
> The problem is that e500 has 2 TLB, so I need to get the tlb index and
> entry index from kvmppc_dtlb_search
> And if kvm_is_visible_gfn() returns nonzero, the two index are needed to
> manipulate TLB0 or TLB1.

OK, sounds reasonable. Feel free to change the prototypes of these hooks
to whatever you need, as long as it's clean and still lets me implement
440.

For example, maybe something like this:
        int kvmppc_dtlb_index(struct kvm_vcpu *vcpu, u32 eaddr);

You could then encode the TLB index in the high bits of the return
index. Alternatively, you could pass &tlb and &index, but I think I like
that less.

-- 
Hollis Blanchard
IBM Linux Technology Center