Re: [PATCH 4/7] kvm mmu: implement necessary data structures for second huge page accounting

[Avi Kivity <avi@redhat.com>]

Joerg Roedel wrote:
> This patch adds the necessary data structures to take care of write
> protections in place within a second huge page sized page.
>
>  
>  struct kvm_vcpu_arch {
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 9936b45..7d4162d 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -390,6 +390,15 @@ static int *slot_largepage_idx(gfn_t gfn, struct kvm_memory_slot *slot)
>  	return &slot->lpage_info[idx].write_count;
>  }
>  
> +static int *slot_hugepage_idx(gfn_t gfn, struct kvm_memory_slot *slot)
> +{
> +	unsigned long idx;
> +
> +	idx = (gfn / KVM_PAGES_PER_1G_PAGE) -
> +	      (slot->base_gfn / KVM_PAGES_PER_1G_PAGE);
> +	return &slot->hpage_info[idx].write_count;
> +}
>   

A page level argument would remove the need for this duplication, as 
well as all the constants.

>  
> +static int has_wrprotected_largepage(struct kvm *kvm, gfn_t gfn)
> +{
> +	struct kvm_memory_slot *slot;
> +	int *hugepage_idx;
> +
> +	gfn = unalias_gfn(kvm, gfn);
> +	slot = gfn_to_memslot_unaliased(kvm, gfn);
> +	if (slot) {
> +		hugepage_idx = slot_hugepage_idx(gfn, slot);
>   

slot_largepage_idx() here?

I don't think we ever write protect large pages, so why is this needed?

> +		return *hugepage_idx;
> +	}
> +
> +	return 1;
> +}
>   


> +
>  static enum kvm_page_size host_page_size(struct kvm *kvm, gfn_t gfn)
>  {
>  	struct vm_area_struct *vma;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 095ebb6..2f05d48 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -103,7 +103,7 @@ struct kvm_memory_slot {
>  	struct {
>  		unsigned long rmap_pde;
>  		int write_count;
> -	} *lpage_info;
> +	} *lpage_info, *hpage_info;
>   

} * lpage_info[KVM_NR_PAGE_LEVELS];

> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 8aa3b95..c4842f4 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1001,10 +1001,14 @@ static void kvm_free_physmem_slot(struct kvm_memory_slot *free,
>  	if (!dont || free->lpage_info != dont->lpage_info)
>  		vfree(free->lpage_info);
>  
> +	if (!dont || free->hpage_info != dont->hpage_info)
> +		vfree(free->hpage_info);
>   

loop

>  void kvm_free_physmem(struct kvm *kvm)
> @@ -1170,6 +1174,28 @@ int __kvm_set_memory_region(struct kvm *kvm,
>  			new.lpage_info[largepages-1].write_count = 1;
>  	}
>  
> +#ifdef KVM_PAGES_PER_LHPAGE
> +	if (npages && !new.hpage_info) {
> +		int hugepages = npages / KVM_PAGES_PER_LHPAGE;
> +		if (npages % KVM_PAGES_PER_LHPAGE)
> +			hugepages++;
> +		if (base_gfn % KVM_PAGES_PER_LHPAGE)
> +			hugepages++;
> +
> +		new.hpage_info = vmalloc(hugepages * sizeof(*new.hpage_info));
> +
> +		if (!new.hpage_info)
> +			goto out_free;
> +
> +		memset(new.hpage_info, 0, hugepages * sizeof(*new.hpage_info));
> +
> +		if (base_gfn % KVM_PAGES_PER_LHPAGE)
> +			new.hpage_info[0].write_count = 1;
> +		if ((base_gfn+npages) % KVM_PAGES_PER_LHPAGE)
> +			new.hpage_info[hugepages-1].write_count = 1;
> +	}
> +#endif
>   

Loop, KVM_NR_PAGE_LEVELS defined per arch.


-- 
error compiling committee.c: too many arguments to function