mm: thp: KVM: Explicitly check for THP when populating secondary MMU

Add a helper, is_transparent_hugepage(), to explicitly check whether a compound page is a THP and use it when populating KVM's secondary MMU. The explicit check fixes a bug where a remapped compound page, e.g. for an XDP Rx socket, is mapped into a KVM guest and is mistaken for a THP, which results in KVM incorrectly creating a huge page in its secondary MMU.

Sean Christopherson committed 6 years ago

Commit 005ba371 parent 22b1d576 files · +31 −9Browse files

Unified · Split

6 files

arch/x86/kvm/mmu/mmu.c +2 −2
include/linux/huge_mm.h +6 −0
include/linux/kvm_host.h +1 −0
mm/huge_memory.c +11 −0
virt/kvm/arm/mmu.c +1 −7
virt/kvm/kvm_main.c +10 −0

arch/x86/kvm/mmu/mmu.c+2−2

@@ -3344,7 +3344,7 @@ static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu, · 3343 unmodified lines
3344	3344	*/
3345	3345	if (!is_error_noslot_pfn(pfn) && !kvm_is_reserved_pfn(pfn) &&
3346	3346	!kvm_is_zone_device_pfn(pfn) && level == PT_PAGE_TABLE_LEVEL &&
3347		− PageTransCompoundMap(pfn_to_page(pfn))) {
	3347	+ kvm_is_transparent_hugepage(pfn)) {
3348	3348	unsigned long mask;
3349	3349
3350	3350	/*
@@ -5961,7 +5961,7 @@ restart: · 2610 unmodified lines
5961	5961	*/
5962	5962	if (sp->role.direct && !kvm_is_reserved_pfn(pfn) &&
5963	5963	!kvm_is_zone_device_pfn(pfn) &&
5964		− PageTransCompoundMap(pfn_to_page(pfn))) {
	5964	+ kvm_is_transparent_hugepage(pfn)) {
5965	5965	pte_list_remove(rmap_head, sptep);
5966	5966
5967	5967	if (kvm_available_flush_tlb_with_range())

include/linux/huge_mm.h+6−0

@@ -160,6 +160,7 @@ extern unsigned long thp_get_unmapped_area(struct file *filp, · 159 unmodified lines
160	160
161	161	extern void prep_transhuge_page(struct page *page);
162	162	extern void free_transhuge_page(struct page *page);
	163	+bool is_transparent_hugepage(struct page *page);
163	164
164	165	bool can_split_huge_page(struct page page, int pextra_pins);
165	166	int split_huge_page_to_list(struct page page, struct list_head list);
@@ -308,6 +309,11 @@ static inline bool transhuge_vma_suitable(struct vm_area_struct *vma, · 142 unmodified lines
308	309
309	310	static inline void prep_transhuge_page(struct page *page) {}
310	311
	312	+static inline bool is_transparent_hugepage(struct page *page)
	313	+{
	314	+ return false;
	315	+}
	316	+
311	317	#define transparent_hugepage_flags 0UL
312	318
313	319	#define thp_get_unmapped_area NULL

include/linux/kvm_host.h+1−0

@@ -976,6 +976,7 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu); · 975 unmodified lines
976	976
977	977	bool kvm_is_reserved_pfn(kvm_pfn_t pfn);
978	978	bool kvm_is_zone_device_pfn(kvm_pfn_t pfn);
	979	+bool kvm_is_transparent_hugepage(kvm_pfn_t pfn);
979	980
980	981	struct kvm_irq_ack_notifier {
981	982	struct hlist_node link;

mm/huge_memory.c+11−0

@@ -527,6 +527,17 @@ void prep_transhuge_page(struct page *page) · 526 unmodified lines
527	527	set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
528	528	}
529	529
	530	+bool is_transparent_hugepage(struct page *page)
	531	+{
	532	+ if (!PageCompound(page))
	533	+ return 0;
	534	+
	535	+ page = compound_head(page);
	536	+ return is_huge_zero_page(page) \|\|
	537	+ page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
	538	+}
	539	+EXPORT_SYMBOL_GPL(is_transparent_hugepage);
	540	+
530	541	static unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
531	542	loff_t off, unsigned long flags, unsigned long size)
532	543	{

virt/kvm/arm/mmu.c+1−7

@@ -1377,14 +1377,8 @@ static bool transparent_hugepage_adjust(kvm_pfn_t pfnp, phys_addr_t ipap) · 1376 unmodified lines
1377	1377	{
1378	1378	kvm_pfn_t pfn = *pfnp;
1379	1379	gfn_t gfn = *ipap >> PAGE_SHIFT;
1380		− struct page *page = pfn_to_page(pfn);
1381	1380
1382		− /*
1383		− * PageTransCompoundMap() returns true for THP and
1384		− * hugetlbfs. Make sure the adjustment is done only for THP
1385		− * pages.
1386		− */
1387		− if (!PageHuge(page) && PageTransCompoundMap(page)) {
	1381	+ if (kvm_is_transparent_hugepage(pfn)) {
1388	1382	unsigned long mask;
1389	1383	/*
1390	1384	* The address we faulted on is backed by a transparent huge

virt/kvm/kvm_main.c+10−0

@@ -191,6 +191,16 @@ bool kvm_is_reserved_pfn(kvm_pfn_t pfn) · 190 unmodified lines
191	191	return true;
192	192	}
193	193
	194	+bool kvm_is_transparent_hugepage(kvm_pfn_t pfn)
	195	+{
	196	+ struct page *page = pfn_to_page(pfn);
	197	+
	198	+ if (!PageTransCompoundMap(page))
	199	+ return false;
	200	+
	201	+ return is_transparent_hugepage(compound_head(page));
	202	+}
	203	+
194	204	/*
195	205	* Switches to specified vcpu, until a matching vcpu_put()
196	206	*/