On Fri, 2008-08-15 at 16:50 +0800, Liu Yu wrote:
> These patches add the support of e500 platform for KVM.
Hi Yu, sorry it's taken me this long to take a look. I've been sick and
catching up from vacation...
> The code is just in the primary stage,
> so this time just for discussion.
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;
booke_fsl_interrupts.S looks like a lot of code copied and pasted, with
the obvious exception of the TLB handlers. Can't we work out some better
way to share the rest?
Christian makes a great point about interrupts in
host_tlb_write_entry(), but I have an even bigger question: by not
tracking the state of the shadow TLB, you're implementing lazy
save/restore. In contrast, 440 is doing a full TLB reload, since I
assume that a) the TLB is so small that is almost certainly full of
useful entries, and b) TLB misses are much more expensive with KVM than
on bare metal.
> I have tested them under branch 2.6.26, but not under the lastest code,
> for my board can not boot up via current kvm tree.
Hmm, that's too bad.
--
Hollis Blanchard
IBM Linux Technology Center
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