KVM: PPC: Book3S HV: Always flush TLB in kvmppc_alloc_reset_hpt()

The KVM_PPC_ALLOCATE_HTAB ioctl(), implemented by kvmppc_alloc_reset_hpt()
is supposed to completely clear and reset a guest's Hashed Page Table (HPT)
allocating or re-allocating it if necessary.

In the case where an HPT of the right size already exists and it just
zeroes it, it forces a TLB flush on all guest CPUs, to remove any stale TLB
entries loaded from the old HPT.

However, that situation can arise when the HPT is resizing as well - or
even when switching from an RPT to HPT - so those cases need a TLB flush as
well.

So, move the TLB flush to trigger in all cases except for errors.

Cc: stable@vger.kernel.org # v4.10+
Fixes: f98a8bf9ee20 ("KVM: PPC: Book3S HV: Allow KVM_PPC_ALLOCATE_HTAB ioctl() to change HPT size")
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 8355398..b73dbc9 100644 (file)
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -165,8 +165,6 @@ long kvmppc_alloc_reset_hpt(struct kvm *kvm, int order)
                 * Reset all the reverse-mapping chains for all memslots
                 */
                kvmppc_rmap_reset(kvm);
-               /* Ensure that each vcpu will flush its TLB on next entry. */
-               cpumask_setall(&kvm->arch.need_tlb_flush);
                err = 0;
                goto out;
        }
@@ -182,6 +180,10 @@ long kvmppc_alloc_reset_hpt(struct kvm *kvm, int order)
        kvmppc_set_hpt(kvm, &info);
 
 out:
+       if (err == 0)
+               /* Ensure that each vcpu will flush its TLB on next entry. */
+               cpumask_setall(&kvm->arch.need_tlb_flush);
+
        mutex_unlock(&kvm->lock);
        return err;
 }