@@ -40,6 +40,8 @@
/* Power architecture requires HPT is at least 256kB */
#define PPC_MIN_HPT_ORDER 18
+static void kvmppc_rmap_reset(struct kvm *kvm);
+
long kvmppc_alloc_hpt(struct kvm *kvm, u32 *htab_orderp)
{
unsigned long hpt;
@@ -137,6 +139,10 @@ long kvmppc_alloc_reset_hpt(struct kvm *kvm, u32 *htab_orderp)
/* Set the entire HPT to 0, i.e. invalid HPTEs */
memset((void *)kvm->arch.hpt_virt, 0, 1ul << order);
/*
+ * Reset all the reverse-mapping chains for all memslots
+ */
+ kvmppc_rmap_reset(kvm);
+ /*
* Set the whole last_vcpu array to an invalid vcpu number.
* This ensures that each vcpu will flush its TLB on next entry.
*/
@@ -756,6 +762,25 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
goto out_put;
}
+static void kvmppc_rmap_reset(struct kvm *kvm)
+{
+ struct kvm_memslots *slots;
+ struct kvm_memory_slot *memslot;
+ int srcu_idx;
+
+ srcu_idx = srcu_read_lock(&kvm->srcu);
+ slots = kvm->memslots;
+ kvm_for_each_memslot(memslot, slots) {
+ /*
+ * This assumes it is acceptable to lose reference and
+ * change bits across a reset.
+ */
+ memset(memslot->arch.rmap, 0,
+ memslot->npages * sizeof(*memslot->arch.rmap));
+ }
+ srcu_read_unlock(&kvm->srcu, srcu_idx);
+}
+
static int kvm_handle_hva_range(struct kvm *kvm,
unsigned long start,
unsigned long end,
With HV-style KVM, we maintain reverse-mapping lists that enable us to find all the HPT (hashed page table) entries that reference each guest physical page, with the heads of the lists in the memslot->arch.rmap arrays. When we reset the HPT (i.e. when we reboot the VM), we clear out all the HPT entries but we were not clearing out the reverse mapping lists. The result is that as we create new HPT entries, the lists get corrupted, which can easily lead to loops, resulting in the host kernel hanging when it tries to traverse those lists. This fixes the problem by zeroing out all the reverse mapping lists when we zero out the HPT. This incidentally means that we are also zeroing our record of the referenced and changed bits (not the bits in the Linux PTEs, used by the Linux MM subsystem, but the bits used by the KVM_GET_DIRTY_LOG ioctl, and those used by kvm_age_hva() and kvm_test_age_hva()). Signed-off-by: Paul Mackerras <paulus@samba.org> Cc: stable@vger.kernel.org --- Since this can cause the host to hang, it should go into Linus' tree ASAP and be backported to 3.6. arch/powerpc/kvm/book3s_64_mmu_hv.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)