The purpose of vhost_section is to identify RAM regions that need to
be made available to a vhost client. However when running under TCG
all RAM sections have DIRTY_MEMORY_CODE set which leads to problems
down the line.
Re-factor the code so:
- steps are clearer to follow
- reason for rejection is recorded in the trace point
- we allow DIRTY_MEMORY_CODE when TCG is enabled
We expand the comment to explain that kernel based vhost has specific
support for migration tracking.
Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
Cc: Michael S. Tsirkin <m...@redhat.com>
Cc: Dr. David Alan Gilbert <dgilb...@redhat.com>
Cc: Stefan Hajnoczi <stefa...@redhat.com>
---
v2
- drop enum, add trace_vhost_reject_section
- return false at any fail point
- unconditionally add DIRTY_MEMORY_CODE to handled cases
- slightly re-word the explanatory comment and commit message
---
hw/virtio/vhost.c | 55 ++++++++++++++++++++++++++++++------------
hw/virtio/trace-events | 3 ++-
2 files changed, 41 insertions(+), 17 deletions(-)
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index aff98a0ede5..120c0cc747b 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -27,6 +27,7 @@
#include "migration/blocker.h"
#include "migration/qemu-file-types.h"
#include "sysemu/dma.h"
+#include "sysemu/tcg.h"
#include "trace.h"
/* enabled until disconnected backend stabilizes */
@@ -403,26 +404,48 @@ static int vhost_verify_ring_mappings(struct vhost_dev
*dev,
return r;
}
+/*
+ * vhost_section: identify sections needed for vhost access
+ *
+ * We only care about RAM sections here (where virtqueue can live). If
+ * we find one we still allow the backend to potentially filter it out
+ * of our list.
+ */
static bool vhost_section(struct vhost_dev *dev, MemoryRegionSection *section)
{
- bool result;
- bool log_dirty = memory_region_get_dirty_log_mask(section->mr) &
- ~(1 << DIRTY_MEMORY_MIGRATION);
- result = memory_region_is_ram(section->mr) &&
- !memory_region_is_rom(section->mr);
-
- /* Vhost doesn't handle any block which is doing dirty-tracking other
- * than migration; this typically fires on VGA areas.
- */
- result &= !log_dirty;
+ MemoryRegion *mr = section->mr;
+
+ if (memory_region_is_ram(mr) && !memory_region_is_rom(mr)) {
+ uint8_t dirty_mask = memory_region_get_dirty_log_mask(mr);
+ uint8_t handled_dirty;
+
+ /*
+ * Kernel based vhost doesn't handle any block which is doing
+ * dirty-tracking other than migration for which it has
+ * specific logging support. However for TCG the kernel never
+ * gets involved anyway so we can also ignore it's
+ * self-modiying code detection flags.
+ */
+ handled_dirty = (1 << DIRTY_MEMORY_MIGRATION);
+ handled_dirty |= (1 << DIRTY_MEMORY_CODE);
- if (result && dev->vhost_ops->vhost_backend_mem_section_filter) {
- result &=
- dev->vhost_ops->vhost_backend_mem_section_filter(dev, section);
- }
+ if (dirty_mask & ~handled_dirty) {
+ trace_vhost_reject_section(mr->name, 1);
+ return false;
+ }
+
+ if (dev->vhost_ops->vhost_backend_mem_section_filter &&
+ !dev->vhost_ops->vhost_backend_mem_section_filter(dev, section)) {
+ trace_vhost_reject_section(mr->name, 2);
+ return false;
+ }
- trace_vhost_section(section->mr->name, result);
- return result;
+ trace_vhost_section(mr->name);
+ return true;
+ } else {
+ trace_vhost_reject_section(mr->name, 3);
+ return false;
+ }
}
static void vhost_begin(MemoryListener *listener)
diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index 84ecb85d445..22427126b97 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -5,7 +5,8 @@ vhost_commit(bool started, bool changed) "Started: %d Changed:
%d"
vhost_region_add_section(const char *name, uint64_t gpa, uint64_t size,
uint64_t host) "%s: 0x%"PRIx64"+0x%"PRIx64" @ 0x%"PRIx64
vhost_region_add_section_merge(const char *name, uint64_t new_size, uint64_t
gpa, uint64_t owr) "%s: size: 0x%"PRIx64 " gpa: 0x%"PRIx64 " owr: 0x%"PRIx64
vhost_region_add_section_aligned(const char *name, uint64_t gpa, uint64_t
size, uint64_t host) "%s: 0x%"PRIx64"+0x%"PRIx64" @ 0x%"PRIx64
-vhost_section(const char *name, int r) "%s:%d"
+vhost_section(const char *name) "%s"
+vhost_reject_section(const char *name, int d) "%s:%d"
vhost_iotlb_miss(void *dev, int step) "%p step %d"
# vhost-user.c
--
2.20.1
