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

Xiao Guangrong
2013-10-24T09:29:53Z

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:

/* 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 */
};