KVM: arm64: Do not try to map PUDs when they are folded into PMD

commit 3fb884ffe921c99483a84b0175f3c03f048e9069 upstream.

For the obscure cases where PMD and PUD are the same size
(64kB pages with 42bit VA, for example, which results in only
two levels of page tables), we can't map anything as a PUD,
because there is... erm... no PUD to speak of. Everything is
either a PMD or a PTE.

So let's only try and map a PUD when its size is different from
that of a PMD.

Cc: stable@vger.kernel.org
Fixes: b8e0ba7c8bea ("KVM: arm64: Add support for creating PUD hugepages at stage 2")
Reported-by: Gavin Shan <gshan@redhat.com>
Reported-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index d1320f3f2b1376efd8d47b0d8913f90f47c4153c..d906350d543ddba712d7ba86d7e03a33680a651a 100644 (file)
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1968,7 +1968,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
                (fault_status == FSC_PERM &&
                 stage2_is_exec(kvm, fault_ipa, vma_pagesize));
 
-       if (vma_pagesize == PUD_SIZE) {
+       /*
+        * If PUD_SIZE == PMD_SIZE, there is no real PUD level, and
+        * all we have is a 2-level page table. Trying to map a PUD in
+        * this case would be fatally wrong.
+        */
+       if (PUD_SIZE != PMD_SIZE && vma_pagesize == PUD_SIZE) {
                pud_t new_pud = kvm_pfn_pud(pfn, mem_type);
 
                new_pud = kvm_pud_mkhuge(new_pud);