Commit 005ba37c authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini

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.

Fixes: 936a5fe6 ("thp: kvm mmu transparent hugepage support")
Reported-by: syzbot+c9d1fb51ac9d0d10c39d@syzkaller.appspotmail.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 22b1d57b
......@@ -3344,7 +3344,7 @@ static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu,
*/
if (!is_error_noslot_pfn(pfn) && !kvm_is_reserved_pfn(pfn) &&
!kvm_is_zone_device_pfn(pfn) && level == PT_PAGE_TABLE_LEVEL &&
PageTransCompoundMap(pfn_to_page(pfn))) {
kvm_is_transparent_hugepage(pfn)) {
unsigned long mask;
/*
......@@ -5961,7 +5961,7 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
*/
if (sp->role.direct && !kvm_is_reserved_pfn(pfn) &&
!kvm_is_zone_device_pfn(pfn) &&
PageTransCompoundMap(pfn_to_page(pfn))) {
kvm_is_transparent_hugepage(pfn)) {
pte_list_remove(rmap_head, sptep);
if (kvm_available_flush_tlb_with_range())
......
......@@ -160,6 +160,7 @@ extern unsigned long thp_get_unmapped_area(struct file *filp,
extern void prep_transhuge_page(struct page *page);
extern void free_transhuge_page(struct page *page);
bool is_transparent_hugepage(struct page *page);
bool can_split_huge_page(struct page *page, int *pextra_pins);
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,
static inline void prep_transhuge_page(struct page *page) {}
static inline bool is_transparent_hugepage(struct page *page)
{
return false;
}
#define transparent_hugepage_flags 0UL
#define thp_get_unmapped_area NULL
......
......@@ -976,6 +976,7 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu);
bool kvm_is_reserved_pfn(kvm_pfn_t pfn);
bool kvm_is_zone_device_pfn(kvm_pfn_t pfn);
bool kvm_is_transparent_hugepage(kvm_pfn_t pfn);
struct kvm_irq_ack_notifier {
struct hlist_node link;
......
......@@ -527,6 +527,17 @@ void prep_transhuge_page(struct page *page)
set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
}
bool is_transparent_hugepage(struct page *page)
{
if (!PageCompound(page))
return 0;
page = compound_head(page);
return is_huge_zero_page(page) ||
page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
}
EXPORT_SYMBOL_GPL(is_transparent_hugepage);
static unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
loff_t off, unsigned long flags, unsigned long size)
{
......
......@@ -1377,14 +1377,8 @@ static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap)
{
kvm_pfn_t pfn = *pfnp;
gfn_t gfn = *ipap >> PAGE_SHIFT;
struct page *page = pfn_to_page(pfn);
/*
* PageTransCompoundMap() returns true for THP and
* hugetlbfs. Make sure the adjustment is done only for THP
* pages.
*/
if (!PageHuge(page) && PageTransCompoundMap(page)) {
if (kvm_is_transparent_hugepage(pfn)) {
unsigned long mask;
/*
* The address we faulted on is backed by a transparent huge
......
......@@ -191,6 +191,16 @@ bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
return true;
}
bool kvm_is_transparent_hugepage(kvm_pfn_t pfn)
{
struct page *page = pfn_to_page(pfn);
if (!PageTransCompoundMap(page))
return false;
return is_transparent_hugepage(compound_head(page));
}
/*
* Switches to specified vcpu, until a matching vcpu_put()
*/
......
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