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Re: [PATCH v26 09/17] vfio: Add load state functions to SaveVMHandlers
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From: |
Kirti Wankhede |
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Subject: |
Re: [PATCH v26 09/17] vfio: Add load state functions to SaveVMHandlers |
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Date: |
Mon, 19 Oct 2020 02:17:43 +0530 |
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User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 |
On 10/1/2020 3:37 PM, Cornelia Huck wrote:
On Wed, 23 Sep 2020 04:54:11 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:
Sequence during _RESUMING device state:
While data for this device is available, repeat below steps:
a. read data_offset from where user application should write data.
b. write data of data_size to migration region from data_offset.
c. write data_size which indicates vendor driver that data is written in
staging buffer.
For user, data is opaque. User should write data in the same order as
received.
Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
hw/vfio/migration.c | 170 +++++++++++++++++++++++++++++++++++++++++++++++++++
hw/vfio/trace-events | 3 +
2 files changed, 173 insertions(+)
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 4611bb972228..ffd70282dd0e 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -328,6 +328,33 @@ static int vfio_save_device_config_state(QEMUFile *f, void
*opaque)
return qemu_file_get_error(f);
}
+static int vfio_load_device_config_state(QEMUFile *f, void *opaque)
+{
+ VFIODevice *vbasedev = opaque;
+ uint64_t data;
+
+ if (vbasedev->ops && vbasedev->ops->vfio_load_config) {
+ int ret;
+
+ ret = vbasedev->ops->vfio_load_config(vbasedev, f);
+ if (ret) {
+ error_report("%s: Failed to load device config space",
+ vbasedev->name);
+ return ret;
+ }
+ }
+
+ data = qemu_get_be64(f);
+ if (data != VFIO_MIG_FLAG_END_OF_STATE) {
+ error_report("%s: Failed loading device config space, "
+ "end flag incorrect 0x%"PRIx64, vbasedev->name, data);
I'm confused here: If we don't have a vfio_load_config callback, or if
that callback did not read everything, we also might end up with a
value that's not END_OF_STATE... in that case, the problem is not with
the stream, but rather with the consumer?
Right, hence "end flag incorrect" is reported.
+ return -EINVAL;
+ }
+
+ trace_vfio_load_device_config_state(vbasedev->name);
+ return qemu_file_get_error(f);
+}
+
/* ---------------------------------------------------------------------- */
static int vfio_save_setup(QEMUFile *f, void *opaque)
@@ -502,12 +529,155 @@ static int vfio_save_complete_precopy(QEMUFile *f, void
*opaque)
return ret;
}
+static int vfio_load_setup(QEMUFile *f, void *opaque)
+{
+ VFIODevice *vbasedev = opaque;
+ VFIOMigration *migration = vbasedev->migration;
+ int ret = 0;
+
+ if (migration->region.mmaps) {
+ ret = vfio_region_mmap(&migration->region);
+ if (ret) {
+ error_report("%s: Failed to mmap VFIO migration region %d: %s",
+ vbasedev->name, migration->region.nr,
+ strerror(-ret));
+ error_report("%s: Falling back to slow path", vbasedev->name);
+ }
+ }
+
+ ret = vfio_migration_set_state(vbasedev, ~VFIO_DEVICE_STATE_MASK,
+ VFIO_DEVICE_STATE_RESUMING);
+ if (ret) {
+ error_report("%s: Failed to set state RESUMING", vbasedev->name);
+ }
+ return ret;
If I follow the code correctly, the cleanup callback will not be
invoked if you return != 0 here... should you clean up possible
mappings on error here?
Makes sense, adding region ummap on error.
+}
+
+static int vfio_load_cleanup(void *opaque)
+{
+ vfio_save_cleanup(opaque);
+ return 0;
+}
+
+static int vfio_load_state(QEMUFile *f, void *opaque, int version_id)
+{
+ VFIODevice *vbasedev = opaque;
+ VFIOMigration *migration = vbasedev->migration;
+ int ret = 0;
+ uint64_t data, data_size;
+
+ data = qemu_get_be64(f);
+ while (data != VFIO_MIG_FLAG_END_OF_STATE) {
+
+ trace_vfio_load_state(vbasedev->name, data);
+
+ switch (data) {
+ case VFIO_MIG_FLAG_DEV_CONFIG_STATE:
+ {
+ ret = vfio_load_device_config_state(f, opaque);
+ if (ret) {
+ return ret;
+ }
+ break;
+ }
+ case VFIO_MIG_FLAG_DEV_SETUP_STATE:
+ {
+ data = qemu_get_be64(f);
+ if (data == VFIO_MIG_FLAG_END_OF_STATE) {
+ return ret;
+ } else {
+ error_report("%s: SETUP STATE: EOS not found 0x%"PRIx64,
+ vbasedev->name, data);
+ return -EINVAL;
+ }
+ break;
+ }
+ case VFIO_MIG_FLAG_DEV_DATA_STATE:
+ {
+ VFIORegion *region = &migration->region;
+ uint64_t data_offset = 0, size;
I think this function would benefit from splitting this off into a
function handling DEV_DATA_STATE. It is quite hard to follow through
all the checks and find out when we continue, and when we break off.
Each switch case has a break, we break off on success cases, where as we
return error if we encounter any case where (ret < 0)
Some documentation about the markers would also be really helpful.
Sure adding it in patch 07, where these are defined.
The logic seems to be:
- DEV_CONFIG_STATE has config data and must be ended by END_OF_STATE
Right
- DEV_SETUP_STATE has only END_OF_STATE, no data
Right now there is no data, but this is provision to add data if
required in future.
- DEV_DATA_STATE has... data; if there's any END_OF_STATE, it's buried
far down in the called functions
This is not correct, END_OF_STATE is after data. Moved data buffer
loading logic to function vfio_load_buffer(), so DEV_DATA_STATE looks
simplified as below. Hope this helps.
case VFIO_MIG_FLAG_DEV_DATA_STATE:
{
uint64_t data_size;
data_size = qemu_get_be64(f);
if (data_size == 0) {
break;
}
ret = vfio_load_buffer(f, vbasedev, data_size);
if (ret < 0) {
return ret;
}
break;
}
Also handling the case if data_size is greater than the data section of
migration region at destination in vfio_load_buffer()in my next version.
Thanks,
Kirti
+
+ data_size = size = qemu_get_be64(f);
+ if (data_size == 0) {
+ break;
+ }
+
+ ret = vfio_mig_read(vbasedev, &data_offset, sizeof(data_offset),
+ region->fd_offset +
+ offsetof(struct vfio_device_migration_info,
+ data_offset));
+ if (ret < 0) {
+ return ret;
+ }
+
+ trace_vfio_load_state_device_data(vbasedev->name, data_offset,
+ data_size);
+
+ while (size) {
+ void *buf = NULL;
+ uint64_t sec_size;
+ bool buf_alloc = false;
+
+ buf = get_data_section_size(region, data_offset, size,
+ &sec_size);
+
+ if (!buf) {
+ buf = g_try_malloc(sec_size);
+ if (!buf) {
+ error_report("%s: Error allocating buffer ", __func__);
+ return -ENOMEM;
+ }
+ buf_alloc = true;
+ }
+
+ qemu_get_buffer(f, buf, sec_size);
+
+ if (buf_alloc) {
+ ret = vfio_mig_write(vbasedev, buf, sec_size,
+ region->fd_offset + data_offset);
+ g_free(buf);
+
+ if (ret < 0) {
+ return ret;
+ }
+ }
+ size -= sec_size;
+ data_offset += sec_size;
+ }
+
+ ret = vfio_mig_write(vbasedev, &data_size, sizeof(data_size),
+ region->fd_offset +
+ offsetof(struct vfio_device_migration_info, data_size));
+ if (ret < 0) {
+ return ret;
+ }
+ break;
+ }
+
+ default:
+ error_report("%s: Unknown tag 0x%"PRIx64, vbasedev->name, data);
+ return -EINVAL;
+ }
+
+ data = qemu_get_be64(f);
+ ret = qemu_file_get_error(f);
+ if (ret) {
+ return ret;
+ }
+ }
+
+ return ret;
+}
+
static SaveVMHandlers savevm_vfio_handlers = {
.save_setup = vfio_save_setup,
.save_cleanup = vfio_save_cleanup,
.save_live_pending = vfio_save_pending,
.save_live_iterate = vfio_save_iterate,
.save_live_complete_precopy = vfio_save_complete_precopy,
+ .load_setup = vfio_load_setup,
+ .load_cleanup = vfio_load_cleanup,
Unrelated to this patch: It's a bit odd that load_cleanup() (unlike
save_cleanup()) has a return code (that seems unused).
+ .load_state = vfio_load_state,
};
/* ---------------------------------------------------------------------- */