kvm, mm: account shadow page tables to kmemcg

The size of kvm's shadow page tables corresponds to the size of the
guest virtual machines on the system.  Large VMs can spend a significant
amount of memory as shadow page tables which can not be left as system
memory overhead.  So, account shadow page tables to the kmemcg.

[shakeelb@google.com: replace (GFP_KERNEL|__GFP_ACCOUNT) with GFP_KERNEL_ACCOUNT]
  Link: http://lkml.kernel.org/r/20180629140224.205849-1-shakeelb@google.com
Link: http://lkml.kernel.org/r/20180627181349.149778-1-shakeelb@google.comSigned-off-by: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/kvm/mmu.c

@@ -890,7 +890,7 @@ static int mmu_topup_memory_cache_page(struct kvm_mmu_memory_cache *cache,
 	if (cache->nobjs >= min)
 		return 0;
 	while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
-		page = (void *)__get_free_page(GFP_KERNEL);
+		page = (void *)__get_free_page(GFP_KERNEL_ACCOUNT);
 		if (!page)
 			return -ENOMEM;
 		cache->objects[cache->nobjs++] = page;