Re: [PATCH v3 10/15] KVM: MMU: allocate shadow pages from slab

Gleb Natapov
2013-10-24T09:52:10Z

On Thu, Oct 24, 2013 at 05:29:44PM +0800, Xiao Guangrong wrote:
> On 10/24/2013 05:19 PM, Gleb Natapov wrote:
>
> >> @@ -946,7 +947,7 @@ static inline struct kvm_mmu_page *page_header(hpa_t shadow_page)
> >> {
> >> struct page *page = pfn_to_page(shadow_page >> PAGE_SHIFT);
> >>
> >> - return (struct kvm_mmu_page *)page_private(page);
> >> + return (struct kvm_mmu_page *)(page->mapping);
> > Why?
>
> That's because page->private has been used by slab:
>
But does lockless path actually looks at it?

> /* Remainder is not double word aligned */
> union {
> unsigned long private; /* Mapping-private opaque data:
> * usually used for buffer_heads
> * if PagePrivate set; used for
> * swp_entry_t if PageSwapCache;
> * indicates order in the buddy
> * system if PG_buddy is set.
> */
> #if USE_SPLIT_PTLOCKS
> spinlock_t ptl;
> #endif
> struct kmem_cache *slab_cache; /* SL[AU]B: Pointer to slab */
> struct page *first_page; /* Compound tail pages */
> };

--
Gleb.