KVM: PPC: Book3S HV: Fix bug leading to deadlock in guest HPT updates

When handling the H_BULK_REMOVE hypercall, we were forgetting to
invalidate and unlock the hashed page table entry (HPTE) in the case
where the page had been paged out.  This fixes it by clearing the
first doubleword of the HPTE in that case.

This fixes a regression introduced in commit a92bce95f0 ("KVM: PPC:
Book3S HV: Keep HPTE locked when invalidating").  The effect of the
regression is that the host kernel will sometimes hang when under
memory pressure.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index def880aea63a34eb0d49dceda27e27c848dffc35..cec4daddbf31632a97cecb23d94d2773ccb8b803 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -463,6 +463,7 @@ long kvmppc_h_bulk_remove(struct kvm_vcpu *vcpu)
                                /* insert R and C bits from PTE */
                                rcbits = rev->guest_rpte & (HPTE_R_R|HPTE_R_C);
                                args[j] |= rcbits << (56 - 5);
+                               hp[0] = 0;
                                continue;
                        }