spapr_iommu: Provide a function to switch a TCE table to allowing VFIO

Because of the way non-VFIO guest IOMMU operations are KVM accelerated, not
all TCE tables (guest IOMMU contexts) can support VFIO devices.  Currently,
this is decided at creation time.

To support hotplug of VFIO devices, we need to allow a TCE table which
previously didn't allow VFIO devices to be switched so that it can.  This
patch adds an spapr_tce_set_need_vfio() function to do this, by
reallocating the table in userspace if necessary.

Currently this doesn't allow the KVM acceleration to be re-enabled if all
the VFIO devices are removed.  That's an optimization for another time.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>

2 files changed, 34 insertions, 0 deletions

diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
index 5166cde..ed28565 100644
--- a/hw/ppc/spapr_iommu.c
+++ b/hw/ppc/spapr_iommu.c
@@ -168,6 +168,38 @@ static int spapr_tce_table_realize(DeviceState *dev)
     return 0;
 }
 
+void spapr_tce_set_need_vfio(sPAPRTCETable *tcet, bool need_vfio)
+{
+    size_t table_size = tcet->nb_table * sizeof(uint64_t);
+    void *newtable;
+
+    if (need_vfio == tcet->need_vfio) {
+        /* Nothing to do */
+        return;
+    }
+
+    if (!need_vfio) {
+        /* FIXME: We don't support transition back to KVM accelerated
+         * TCEs yet */
+        return;
+    }
+
+    tcet->need_vfio = true;
+
+    if (tcet->fd < 0) {
+        /* Table is already in userspace, nothing to be do */
+        return;
+    }
+
+    newtable = g_malloc(table_size);
+    memcpy(newtable, tcet->table, table_size);
+
+    kvmppc_remove_spapr_tce(tcet->table, tcet->fd, tcet->nb_table);
+
+    tcet->fd = -1;
+    tcet->table = newtable;
+}
+
 sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn,
                                    uint64_t bus_offset,
                                    uint32_t page_shift,
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 27d65d5..5baa906 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -589,6 +589,8 @@ sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn,
                                    uint32_t page_shift,
                                    uint32_t nb_table,
                                    bool need_vfio);
+void spapr_tce_set_need_vfio(sPAPRTCETable *tcet, bool need_vfio);
+
 MemoryRegion *spapr_tce_get_iommu(sPAPRTCETable *tcet);
 int spapr_dma_dt(void *fdt, int node_off, const char *propname,
                  uint32_t liobn, uint64_t window, uint32_t size);