Subject: Re: [PATCH 1/2] KVM: PPC: Add generic hpte management functions

From: Alexander Graf <[email-masked]>
Date: Tue, 22 Jun 2010 14:04:24 +0200

Avi Kivity wrote:
> On 06/21/2010 04:44 PM, Alexander Graf wrote:
>> Currently the shadow paging code keeps an array of entries it knows
>> about.
>> Whenever the guest invalidates an entry, we loop through that entry,
>> trying to invalidate matching parts.
>>
>> While this is a really simple implementation, it is probably the most
>> ineffective one possible. So instead, let's keep an array of lists
>> around
>> that are indexed by a hash. This way each PTE can be added by 4
>> list_add,
>> removed by 4 list_del invocations and the search only needs to loop
>> through
>> entries that share the same hash.
>>
>> This patch implements said lookup and exports generic functions that
>> both
>> the 32-bit and 64-bit backend can use.
>>    
>
> Mind explaining the all list in there?

The all list is used to flush all entries when we need to get rid of all
entries, for example when we write a BAT.

>
>>
>> +
>> +static inline u64 kvmppc_mmu_hash_pte(u64 eaddr) {
>> +    return hash_64(eaddr>>  PTE_SIZE, HPTEG_HASH_BITS);
>> +}
>> +
>> +static inline u64 kvmppc_mmu_hash_vpte(u64 vpage) {
>> +    return hash_64(vpage&  0xfffffffffULL, HPTEG_HASH_BITS);
>> +}
>> +
>> +static inline u64 kvmppc_mmu_hash_vpte_long(u64 vpage) {
>> +    return hash_64((vpage&  0xffffff000ULL)>>  12, HPTEG_HASH_BITS);
>> +}
>>    
>
> Please use ordinary formatting for the functions above.

Ouch.

>
>> +/* Flush with mask 0xffffff000 */
>> +static void kvmppc_mmu_pte_vflush_long(struct kvm_vcpu *vcpu, u64
>> guest_vp)
>> +{
>> +    struct list_head *list;
>> +    struct hpte_cache *pte, *tmp;
>> +    u64 vp_mask = 0xffffff000ULL;
>> +
>> +    list
>> =&vcpu->arch.hpte_hash_vpte_long[kvmppc_mmu_hash_vpte_long(guest_vp)];
>> +
>> +    /* No entries to flush */
>> +    if (!list)
>> +        return;
>> +
>> +    /* Check the list for matching entries */
>> +    list_for_each_entry_safe(pte, tmp, list, list_vpte_long)
>> +        /* Jump over the helper entry */
>> +        if (&pte->list_vpte_long == list)
>> +            continue;
>> +
>> +        if ((pte->pte.vpage&  vp_mask) == guest_vp)
>> +            invalidate_pte(vcpu, pte);
>> +}
>>    
>
> C wants brackets around blocks.
>

Even more ouch.

Alex