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hw/virtio/vhost: re-factor vhost-section and allow DIRTY_MEMORY_CODE 

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

We expand the comment to explain that kernel based vhost has specific
support for migration tracking.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Fabiano Rosas <farosas@linux.ibm.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200605154929.26910-11-alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2020-06-05 16:49:25 +01:00
parent a97098844b
commit 083b9bd7a1
2 changed files with 42 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
hw/virtio/trace-events
View File

@ -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

55
hw/virtio/vhost.c
View File

@ -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 +404,50 @@ 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 and guest
* internals accessed by virtio might 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);
MemoryRegion *mr = 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;
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;
if (result && dev->vhost_ops->vhost_backend_mem_section_filter) {
result &=
dev->vhost_ops->vhost_backend_mem_section_filter(dev, section);
/*
* 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. However a vhost-user
* client could still confuse a TCG guest if it re-writes
* executable memory that has already been translated.
*/
handled_dirty = (1 << DIRTY_MEMORY_MIGRATION) |
(1 << DIRTY_MEMORY_CODE);
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(mr->name);
return true;
} else {
trace_vhost_reject_section(mr->name, 3);
return false;
}
trace_vhost_section(section->mr->name, result);
return result;
}
static void vhost_begin(MemoryListener *listener)