On 18.01.2013, at 01:20, Alexander Graf wrote:
>
> On 18.01.2013, at 01:11, Scott Wood wrote:
>
>> On 01/17/2013 04:50:39 PM, Alexander Graf wrote:
>>> @@ -1024,9 +1001,11 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 eaddr, gpa_t gpaddr,
>>> {
>>> struct kvmppc_vcpu_e500 *vcpu_e500 = to_e500(vcpu);
>>> struct tlbe_priv *priv;
>>> - struct kvm_book3e_206_tlb_entry *gtlbe, stlbe;
>>> + struct kvm_book3e_206_tlb_entry *gtlbe, stlbe = {};
>>
>> Is there a code path in which stlbe gets used but not fully filled in
>> without this?
>
> I am hoping not, but when I wrote this patch gcc suddenly jumped at me claiming that the whole struct can get used uninitialized:
>
> arch/powerpc/kvm/e500_mmu_host.c: In function ‘kvmppc_mmu_map’:
> arch/powerpc/kvm/e500_mmu_host.c:533: error: ‘stlbe.mas1’ may be used uninitialized in this function
> arch/powerpc/kvm/e500_mmu_host.c:533: error: ‘stlbe.mas2’ may be used uninitialized in this function
> arch/powerpc/kvm/e500_mmu_host.c:533: error: ‘stlbe.mas7_3’ may be used uninitialized in this function
> arch/powerpc/kvm/e500_mmu_host.c:533: error: ‘stlbe.mas8’ may be used uninitialized in this function
>
> If you have any idea where this could come from, please let me know :).
>
>>
>>> int tlbsel = tlbsel_of(index);
>>> int esel = esel_of(index);
>>> + /* Needed for initial map, where we can't use the cached value */
>>> + int force_map = index & KVM_E500_INDEX_FORCE_MAP;
>>> int stlbsel, sesel;
>>> gtlbe = get_entry(vcpu_e500, tlbsel, esel);
>>> @@ -1038,7 +1017,7 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 eaddr, gpa_t gpaddr,
>>> priv = &vcpu_e500->gtlb_priv[tlbsel][esel];
>>> /* Only triggers after clear_tlb_refs */
>>> - if (unlikely(!(priv->ref.flags & E500_TLB_VALID)))
>>> + if (force_map || unlikely(!(priv->ref.flags & E500_TLB_VALID)))
>>> kvmppc_e500_tlb0_map(vcpu_e500, esel, &stlbe);
>>> else
>>> kvmppc_e500_setup_stlbe(vcpu, gtlbe, BOOK3E_PAGESZ_4K,
>>
>> It seems a bit odd to overload index rather than adding a flags
>> parameter...
>
> Yeah, I mostly wanted to refrain from touching 440 code. But if you prefer that, I can certainly do so :).
>
>> It also seems like it would be cleaner to just invalidate the old entry
>> in tlbwe, and then this function doesn't need to change at all. I am a
>> bit confused by how invalidation is currently operating
Well, this bit is obvious. It's done by kvmppc_e500_shadow_map when it calls kvmppc_e500_ref_release(), right?
Why it's not done explicitly though is a really good question :).
Alex
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