On Wed, Dec 23, 2009 at 02:32:55PM +0200, Avi Kivity wrote:
> On 12/23/2009 01:38 PM, Marcelo Tosatti wrote:
>> Use two steps for memslot deletion: mark the slot invalid (which stops
>> instantiation of new shadow pages for that slot, but allows destruction),
>> then instantiate the new empty slot.
>>
>> Also simplifies kvm_handle_hva locking.
>>
>>
>> r = kvm_arch_prepare_memory_region(kvm,&new, old, user_alloc);
>> if (r)
>> goto out_free;
>>
>
> r == 0
Huh? kvm_arch_prepare_memory_region returns a suitable error code on
failure, 0 on success.
>>
>> - spin_lock(&kvm->mmu_lock);
>> - if (mem->slot>= kvm->memslots->nmemslots)
>> - kvm->memslots->nmemslots = mem->slot + 1;
>> +#ifdef CONFIG_DMAR
>> + /* map the pages in iommu page table */
>> + if (npages)
>> + r = kvm_iommu_map_pages(kvm,&new);
>> + if (r)
>> + goto out_free;
>>
>
> Bad indentation.
>
> (still r == 0)
kvm_iommu_map_pages returns 0 on success, error code otherwise? The
error code of kvm_iommu_map_pages was returned before the patchset, BTW.
>> +#endif
>>
>> - *memslot = new;
>> - spin_unlock(&kvm->mmu_lock);
>> + slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
>> + if (!slots)
>> + goto out_free;
>>
>
> goto out_free with r == 0.
>
> Best to assign r = -ENOMEM each time, to avoid these headaches.
Fixed.
>> +int memslot_id(struct kvm *kvm, gfn_t gfn)
>>
>
> Should be either static or kvm_memslot_id(). But the source is already
> like that, so leave it.
OK.
>> @@ -807,23 +808,18 @@ static int kvm_handle_hva(struct kvm *kv
>> int (*handler)(struct kvm *kvm, unsigned long *rmapp,
>> unsigned long data))
>> {
>> - int i, j;
>> + int i, j, idx;
>> int retval = 0;
>> - struct kvm_memslots *slots = kvm->memslots;
>> + struct kvm_memslots *slots;
>> +
>> + idx = srcu_read_lock(&kvm->srcu);
>>
>
> Maybe a better place is in the mmu notifiers, so the code is shared
> (once other archs start to use mmu notifiers).
Done.
>> @@ -3020,16 +3017,20 @@ nomem:
>> */
>> unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm)
>> {
>> - int i;
>> + int i, idx;
>> unsigned int nr_mmu_pages;
>> unsigned int nr_pages = 0;
>> + struct kvm_memslots *slots;
>>
>> - for (i = 0; i< kvm->memslots->nmemslots; i++)
>> - nr_pages += kvm->memslots->memslots[i].npages;
>> + idx = srcu_read_lock(&kvm->srcu);
>> + slots = rcu_dereference(kvm->memslots);
>> + for (i = 0; i< slots->nmemslots; i++)
>> + nr_pages += slots->memslots[i].npages;
>>
>> nr_mmu_pages = nr_pages * KVM_PERMILLE_MMU_PAGES / 1000;
>> nr_mmu_pages = max(nr_mmu_pages,
>> (unsigned int) KVM_MIN_ALLOC_MMU_PAGES);
>> + srcu_read_unlock(&kvm->srcu, idx);
>>
>>
>
> Again, would like to move the srcu_locking to an outer scope.
This one was for documentation purposes only, since
kvm_mmu_calculate_mmu_pages is only called from commit_memory_region
(which mutually excludes itself).
I can remove it if you'd prefer.
>> @@ -1503,10 +1504,18 @@ static void enter_pmode(struct kvm_vcpu
>> static gva_t rmode_tss_base(struct kvm *kvm)
>> {
>> if (!kvm->arch.tss_addr) {
>> - gfn_t base_gfn = kvm->memslots->memslots[0].base_gfn +
>> - kvm->memslots->memslots[0].npages - 3;
>> + struct kvm_memslots *slots;
>> + gfn_t base_gfn;
>> + int idx;
>> +
>> + idx = srcu_read_lock(&kvm->srcu);
>> + slots = rcu_dereference(kvm->memslots);
>> + base_gfn = slots->memslots[0].base_gfn +
>> + slots->memslots[0].npages - 3;
>> + srcu_read_unlock(&kvm->srcu, idx);
>> return base_gfn<< PAGE_SHIFT;
>> }
>> +
>> return kvm->arch.tss_addr;
>> }
>>
>
> Shouldn't we already hold the srcu_lock as part of normal guest exit
> (similar to down_read() we do today)?
Yes, but:
kvm_arch_vcpu_setup -> vmx_vcpu_reset -> vmx_set_cr0 -> enter_pmode
So its called outside guest context path (memslot info is used outside
guest context in this case).
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