On Thu, May 11, 2017 at 04:35:21PM +0800, Jason Wang wrote:
>
>
> On 2017年05月10日 16:01, Peter Xu wrote:
> >This patch pre-heat vhost iotlb cache when passthrough mode enabled.
> >
> >Sometimes, even if user specified iommu_platform for vhost devices,
> >IOMMU might still be disabled. One case is passthrough mode in VT-d
> >implementation. We can detect this by observing iommu_list. If it's
> >empty, it means IOMMU translation is disabled, then we can actually
> >pre-heat the translation (it'll be static mapping then) by first
> >invalidating all IOTLB, then cache existing memory ranges into vhost
> >backend iotlb using 1:1 mapping.
> >
> >Signed-off-by: Peter Xu <pet...@redhat.com>
> >---
> > hw/virtio/trace-events | 4 ++++
> > hw/virtio/vhost.c | 49
> > +++++++++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 53 insertions(+)
> >
> >diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> >index 1f7a7c1..54dcbb3 100644
> >--- a/hw/virtio/trace-events
> >+++ b/hw/virtio/trace-events
> >@@ -24,3 +24,7 @@ virtio_balloon_handle_output(const char *name, uint64_t
> >gpa) "section name: %s g
> > virtio_balloon_get_config(uint32_t num_pages, uint32_t actual) "num_pages:
> > %d actual: %d"
> > virtio_balloon_set_config(uint32_t actual, uint32_t oldactual) "actual: %d
> > oldactual: %d"
> > virtio_balloon_to_target(uint64_t target, uint32_t num_pages) "balloon
> > target: %"PRIx64" num_pages: %d"
> >+
> >+# hw/virtio/vhost.c
> >+vhost_iommu_commit(void) ""
> >+vhost_iommu_static_preheat(void) ""
> >diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> >index 0001e60..1c92e62 100644
> >--- a/hw/virtio/vhost.c
> >+++ b/hw/virtio/vhost.c
> >@@ -27,6 +27,7 @@
> > #include "hw/virtio/virtio-access.h"
> > #include "migration/migration.h"
> > #include "sysemu/dma.h"
> >+#include "trace.h"
> > /* enabled until disconnected backend stabilizes */
> > #define _VHOST_DEBUG 1
> >@@ -730,6 +731,11 @@ static void vhost_iommu_unmap_notify(IOMMUNotifier *n,
> >IOMMUTLBEntry *iotlb)
> > }
> > }
> >+static bool vhost_iommu_mr_enabled(struct vhost_dev *dev)
> >+{
> >+ return !QLIST_EMPTY(&dev->iommu_list);
> >+}
> >+
> > static void vhost_iommu_region_add(MemoryListener *listener,
> > MemoryRegionSection *section)
> > {
> >@@ -782,6 +788,48 @@ static void vhost_iommu_region_del(MemoryListener
> >*listener,
> > }
> > }
> >+static void vhost_iommu_commit(MemoryListener *listener)
> >+{
> >+ struct vhost_dev *dev = container_of(listener, struct vhost_dev,
> >+ iommu_listener);
> >+ struct vhost_memory_region *r;
> >+ int i;
> >+
> >+ trace_vhost_iommu_commit();
> >+
> >+ if (!vhost_iommu_mr_enabled(dev)) {
> >+ /*
> >+ * This means iommu_platform is enabled, however iommu memory
> >+ * region is disabled, e.g., when device passthrough is setup.
> >+ * Then, no translation is needed any more.
> >+ *
> >+ * Let's first invalidate the whole IOTLB, then pre-heat the
> >+ * static mapping by looping over vhost memory ranges.
> >+ */
> >+
> >+ if (dev->vhost_ops->vhost_invalidate_device_iotlb(dev, 0,
> >+ UINT64_MAX-1)) {
> >+ error_report("%s: flush existing IOTLB failed", __func__);
> >+ return;
> >+ }
> >+
> >+ for (i = 0; i < dev->mem->nregions; i++) {
> >+ r = &dev->mem->regions[i];
> >+ /* Vhost regions are writable RAM, so IOMMU_RW suites. */
> >+ if (dev->vhost_ops->vhost_update_device_iotlb(dev,
> >+
> >r->guest_phys_addr,
> >+ r->userspace_addr,
> >+ r->memory_size,
> >+ IOMMU_RW)) {
> >+ error_report("%s: pre-heat static mapping failed",
> >__func__);
> >+ return;
> >+ }
> >+ }
> >+
> >+ trace_vhost_iommu_static_preheat();
> >+ }
> >+}
>
> Looks like vfio does the map in region_add(), if we can have different types
> of memory regions (e.g some were under an IOMMU but others were not), do we
> need to switch to do this in vhost_iommu_region_add() ?
Currently this is only a pre-heat of cache only if IOMMU is totally
disabled (!vhost_iommu_mr_enabled(dev) means no IOMMU memory regions).
This patch won't be activated without this condition, so for the cases
(non-x86 platforms) where there are some IOMMU regions, it'll be just
automatically disabled. And, I don't really quite sure whether we
should cache non-IOMMU regions when there are some IOMMU regions... So
imho we can keep this until one day we really want to support some
non-x86 platforms for vhost-dmar, then we can work on top. Thanks,
--
Peter Xu
