Commit 083b9bd7 authored by Alex Bennée's avatar Alex Bennée
Browse files

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: default avatarAlex Bennée <alex.bennee@linaro.org>
Tested-by: default avatarFabiano 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>
parent a9709884

hw/virtio/trace-events

+2 −1
Original line number Diff line number Diff line
@@ -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

hw/virtio/vhost.c

+41 −16
Original line number Diff line number Diff line
@@ -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);



    /* Vhost doesn't handle any block which is doing dirty-tracking other

     * than migration; this typically fires on VGA areas.

    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. However a vhost-user

         * client could still confuse a TCG guest if it re-writes

         * executable memory that has already been translated.

         */

    result &= !log_dirty;

        handled_dirty = (1 << DIRTY_MEMORY_MIGRATION) |

            (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;

        }



    trace_vhost_section(section->mr->name, result);

    return result;

        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;

    }

}



static void vhost_begin(MemoryListener *listener)