Re: [patch 07/10] KVM: MMU: mmu_parent_walk

Marcelo Tosatti
2008-09-22T22:05:30Z

On Mon, Sep 22, 2008 at 11:30:51PM +0300, Avi Kivity wrote:
> Marcelo Tosatti wrote:
>> On Fri, Sep 19, 2008 at 05:56:46PM -0700, Avi Kivity wrote:
>>
>>>> + } while (level > start_level-1);
>>>> +}
>>>> +
>>>>
>>> Could be much simplified with recursion, no? As the depth is limited
>>> to 4, there's no stack overflow problem.
>>>
>>
>> The early version was recursive, but since its a generic helper I
>> preferred a non-recursive function.
>>
>
> Let's start with a super-simple recursive version. When the code has
> seen some debugging, we can add complexity. But for the initial phase,
> simpler is better.
>
> The non-recursive version has the advantage that it can be converted to
> a kvm_for_each_parent() later, but still, we can do that later.

OK, this is the earlier version. I'll resend the patchset with it
instead, anything else? (hoping you're ok with 32-bit nonpae being done
as optimization later).

Index: kvm.oos2/arch/x86/kvm/mmu.c
===================================================================
--- kvm.oos2.orig/arch/x86/kvm/mmu.c
+++ kvm.oos2/arch/x86/kvm/mmu.c
@@ -922,6 +922,31 @@ static void mmu_page_remove_parent_pte(s
BUG();
}

+static int mmu_parent_walk(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
+ int (*fn) (struct kvm_vcpu *vcpu,
+ struct kvm_mmu_page *sp))
+{
+ struct kvm_pte_chain *pte_chain;
+ struct hlist_node *node;
+ struct kvm_mmu_page *parent_sp;
+ int i;
+
+ fn(vcpu, sp);
+
+ if (!sp->multimapped && sp->parent_pte) {
+ parent_sp = page_header(__pa(sp->parent_pte));
+ mmu_parent_walk(vcpu, parent_sp, fn);
+ return;
+ }
+ hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)
+ for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
+ if (!pte_chain->parent_ptes[i])
+ break;
+ parent_sp = page_header(__pa(pte_chain->parent_ptes[i]));
+ mmu_parent_walk(vcpu, parent_sp, fn);
+ }
+}
+
static void nonpaging_prefetch_page(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp)
{