From: Kirti Wankhede <kwankhede@nvidia.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Zhengxiao.zx@Alibaba-inc.com, kevin.tian@intel.com,
yi.l.liu@intel.com, cjia@nvidia.com, eskultet@redhat.com,
ziye.yang@intel.com, qemu-devel@nongnu.org, cohuck@redhat.com,
shuangtai.tst@alibaba-inc.com, dgilbert@redhat.com,
zhi.a.wang@intel.com, mlevitsk@redhat.com, pasic@linux.ibm.com,
aik@ozlabs.ru, eauger@redhat.com, felipe@nutanix.com,
jonathan.davies@nutanix.com, yan.y.zhao@intel.com,
changpeng.liu@intel.com, Ken.Xue@amd.com
Subject: Re: [Qemu-devel] [PATCH v4 08/13] vfio: Add save state functions to SaveVMHandlers
Date: Sat, 22 Jun 2019 01:08:40 +0530 [thread overview]
Message-ID: <b345a59c-b34d-c589-be78-b7a7690e80b2@nvidia.com> (raw)
In-Reply-To: <20190621091638.18127e7a@x1.home>
On 6/21/2019 8:46 PM, Alex Williamson wrote:
> On Fri, 21 Jun 2019 12:08:26 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>
>> On 6/21/2019 12:55 AM, Alex Williamson wrote:
>>> On Thu, 20 Jun 2019 20:07:36 +0530
>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>>>
>>>> Added .save_live_pending, .save_live_iterate and .save_live_complete_precopy
>>>> functions. These functions handles pre-copy and stop-and-copy phase.
>>>>
>>>> In _SAVING|_RUNNING device state or pre-copy phase:
>>>> - read pending_bytes
>>>> - read data_offset - indicates kernel driver to write data to staging
>>>> buffer which is mmapped.
>>>
>>> Why is data_offset the trigger rather than data_size? It seems that
>>> data_offset can't really change dynamically since it might be mmap'd,
>>> so it seems unnatural to bother re-reading it.
>>>
>>
>> Vendor driver can change data_offset, he can have different data_offset
>> for device data and dirty pages bitmap.
>>
>>>> - read data_size - amount of data in bytes written by vendor driver in migration
>>>> region.
>>>> - if data section is trapped, pread() number of bytes in data_size, from
>>>> data_offset.
>>>> - if data section is mmaped, read mmaped buffer of size data_size.
>>>> - Write data packet to file stream as below:
>>>> {VFIO_MIG_FLAG_DEV_DATA_STATE, data_size, actual data,
>>>> VFIO_MIG_FLAG_END_OF_STATE }
>>>>
>>>> In _SAVING device state or stop-and-copy phase
>>>> a. read config space of device and save to migration file stream. This
>>>> doesn't need to be from vendor driver. Any other special config state
>>>> from driver can be saved as data in following iteration.
>>>> b. read pending_bytes - indicates kernel driver to write data to staging
>>>> buffer which is mmapped.
>>>
>>> Is it pending_bytes or data_offset that triggers the write out of
>>> data? Why pending_bytes vs data_size? I was interpreting
>>> pending_bytes as the total data size while data_size is the size
>>> available to read now, so assumed data_size would be more closely
>>> aligned to making the data available.
>>>
>>
>> Sorry, that's my mistake while editing, its read data_offset as in above
>> case.
>>
>>>> c. read data_size - amount of data in bytes written by vendor driver in
>>>> migration region.
>>>> d. if data section is trapped, pread() from data_offset of size data_size.
>>>> e. if data section is mmaped, read mmaped buffer of size data_size.
>>>
>>> Should this read as "pread() from data_offset of data_size, or
>>> optionally if mmap is supported on the data area, read data_size from
>>> start of mapped buffer"? IOW, pread should always work. Same in
>>> previous section.
>>>
>>
>> ok. I'll update.
>>
>>>> f. Write data packet as below:
>>>> {VFIO_MIG_FLAG_DEV_DATA_STATE, data_size, actual data}
>>>> g. iterate through steps b to f until (pending_bytes > 0)
>>>
>>> s/until/while/
>>
>> Ok.
>>
>>>
>>>> h. Write {VFIO_MIG_FLAG_END_OF_STATE}
>>>>
>>>> .save_live_iterate runs outside the iothread lock in the migration case, which
>>>> could race with asynchronous call to get dirty page list causing data corruption
>>>> in mapped migration region. Mutex added here to serial migration buffer read
>>>> operation.
>>>
>>> Would we be ahead to use different offsets within the region for device
>>> data vs dirty bitmap to avoid this?
>>>
>>
>> Lock will still be required to serialize the read/write operations on
>> vfio_device_migration_info structure in the region.
>>
>>
>>>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>>>> Reviewed-by: Neo Jia <cjia@nvidia.com>
>>>> ---
>>>> hw/vfio/migration.c | 212 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>> 1 file changed, 212 insertions(+)
>>>>
>>>> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
>>>> index fe0887c27664..0a2f30872316 100644
>>>> --- a/hw/vfio/migration.c
>>>> +++ b/hw/vfio/migration.c
>>>> @@ -107,6 +107,111 @@ static int vfio_migration_set_state(VFIODevice *vbasedev, uint32_t state)
>>>> return 0;
>>>> }
>>>>
>>>> +static int vfio_save_buffer(QEMUFile *f, VFIODevice *vbasedev)
>>>> +{
>>>> + VFIOMigration *migration = vbasedev->migration;
>>>> + VFIORegion *region = &migration->region.buffer;
>>>> + uint64_t data_offset = 0, data_size = 0;
>>>> + int ret;
>>>> +
>>>> + ret = pread(vbasedev->fd, &data_offset, sizeof(data_offset),
>>>> + region->fd_offset + offsetof(struct vfio_device_migration_info,
>>>> + data_offset));
>>>> + if (ret != sizeof(data_offset)) {
>>>> + error_report("Failed to get migration buffer data offset %d",
>>>> + ret);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> + ret = pread(vbasedev->fd, &data_size, sizeof(data_size),
>>>> + region->fd_offset + offsetof(struct vfio_device_migration_info,
>>>> + data_size));
>>>> + if (ret != sizeof(data_size)) {
>>>> + error_report("Failed to get migration buffer data size %d",
>>>> + ret);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> + if (data_size > 0) {
>>>> + void *buf = NULL;
>>>> + bool buffer_mmaped = false;
>>>> +
>>>> + if (region->mmaps) {
>>>> + int i;
>>>> +
>>>> + for (i = 0; i < region->nr_mmaps; i++) {
>>>> + if ((data_offset >= region->mmaps[i].offset) &&
>>>> + (data_offset < region->mmaps[i].offset +
>>>> + region->mmaps[i].size)) {
>>>> + buf = region->mmaps[i].mmap + (data_offset -
>>>> + region->mmaps[i].offset);
>>>
>>> So you're expecting that data_offset is somewhere within the data
>>> area. Why doesn't the data always simply start at the beginning of the
>>> data area? ie. data_offset would coincide with the beginning of the
>>> mmap'able area (if supported) and be static. Does this enable some
>>> functionality in the vendor driver?
>>
>> Do you want to enforce that to vendor driver?
>> From the feedback on previous version I thought vendor driver should
>> define data_offset within the region
>> "I'd suggest that the vendor driver expose a read-only
>> data_offset that matches a sparse mmap capability entry should the
>> driver support mmap. The use should always read or write data from the
>> vendor defined data_offset"
>>
>> This also adds flexibility to vendor driver such that vendor driver can
>> define different data_offset for device data and dirty page bitmap
>> within same mmaped region.
>
> I agree, it adds flexibility, the protocol was not evident to me until
> I got here though.
>
>>> Does resume data need to be
>>> written from the same offset where it's read?
>>
>> No, resume data should be written from the data_offset that vendor
>> driver provided during resume.
>
> s/resume/save/?
>
> Or is this saying that on resume that the vendor driver is requesting a
> specific block of data via data_offset?
Correct.
Thanks,
Kirti
> I think resume is going to be
> directed by the user, writing in the same order they received the
> data. Thanks,
>
> Alex
>
>>>> + buffer_mmaped = true;
>>>> + break;
>>>> + }
>>>> + }
>>>> + }
>>>> +
>>>> + if (!buffer_mmaped) {
>>>> + buf = g_malloc0(data_size);
>>>> + ret = pread(vbasedev->fd, buf, data_size,
>>>> + region->fd_offset + data_offset);
>>>> + if (ret != data_size) {
>>>> + error_report("Failed to get migration data %d", ret);
>>>> + g_free(buf);
>>>> + return -EINVAL;
>>>> + }
>>>> + }
>>>> +
>>>> + qemu_put_be64(f, data_size);
>>>> + qemu_put_buffer(f, buf, data_size);
>>>> +
>>>> + if (!buffer_mmaped) {
>>>> + g_free(buf);
>>>> + }
>>>> + migration->pending_bytes -= data_size;
>>>> + } else {
>>>> + qemu_put_be64(f, data_size);
>>>> + }
>>>> +
>>>> + ret = qemu_file_get_error(f);
>>>> +
>>>> + return data_size;
>>>> +}
>>>> +
>>>> +static int vfio_update_pending(VFIODevice *vbasedev)
>>>> +{
>>>> + VFIOMigration *migration = vbasedev->migration;
>>>> + VFIORegion *region = &migration->region.buffer;
>>>> + uint64_t pending_bytes = 0;
>>>> + int ret;
>>>> +
>>>> + ret = pread(vbasedev->fd, &pending_bytes, sizeof(pending_bytes),
>>>> + region->fd_offset + offsetof(struct vfio_device_migration_info,
>>>> + pending_bytes));
>>>
>>> Did this trigger the vendor driver to write out to the data area when
>>> we don't need it to?
>>>
>>
>> No, as I mentioned above, I'll update the description.
>>
>> Thanks,
>> Kirti
>>
>>>> + if ((ret < 0) || (ret != sizeof(pending_bytes))) {
>>>> + error_report("Failed to get pending bytes %d", ret);
>>>> + migration->pending_bytes = 0;
>>>> + return (ret < 0) ? ret : -EINVAL;
>>>> + }
>>>> +
>>>> + migration->pending_bytes = pending_bytes;
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static int vfio_save_device_config_state(QEMUFile *f, void *opaque)
>>>> +{
>>>> + VFIODevice *vbasedev = opaque;
>>>> +
>>>> + qemu_put_be64(f, VFIO_MIG_FLAG_DEV_CONFIG_STATE);
>>>> +
>>>> + if (vbasedev->type == VFIO_DEVICE_TYPE_PCI) {
>>>> + vfio_pci_save_config(vbasedev, f);
>>>> + }
>>>> + qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
>>>> +
>>>> + return qemu_file_get_error(f);
>>>> +}
>>>> +
>>>> /* ---------------------------------------------------------------------- */
>>>>
>>>> static int vfio_save_setup(QEMUFile *f, void *opaque)
>>>> @@ -163,9 +268,116 @@ static void vfio_save_cleanup(void *opaque)
>>>> }
>>>> }
>>>>
>>>> +static void vfio_save_pending(QEMUFile *f, void *opaque,
>>>> + uint64_t threshold_size,
>>>> + uint64_t *res_precopy_only,
>>>> + uint64_t *res_compatible,
>>>> + uint64_t *res_postcopy_only)
>>>> +{
>>>> + VFIODevice *vbasedev = opaque;
>>>> + VFIOMigration *migration = vbasedev->migration;
>>>> + int ret;
>>>> +
>>>> + ret = vfio_update_pending(vbasedev);
>>>> + if (ret) {
>>>> + return;
>>>> + }
>>>> +
>>>> + if (vbasedev->device_state & VFIO_DEVICE_STATE_RUNNING) {
>>>> + *res_precopy_only += migration->pending_bytes;
>>>> + } else {
>>>> + *res_postcopy_only += migration->pending_bytes;
>>>> + }
>>>> + *res_compatible += 0;
>>>> +}
>>>> +
>>>> +static int vfio_save_iterate(QEMUFile *f, void *opaque)
>>>> +{
>>>> + VFIODevice *vbasedev = opaque;
>>>> + VFIOMigration *migration = vbasedev->migration;
>>>> + int ret;
>>>> +
>>>> + qemu_put_be64(f, VFIO_MIG_FLAG_DEV_DATA_STATE);
>>>> +
>>>> + qemu_mutex_lock(&migration->lock);
>>>> + ret = vfio_save_buffer(f, vbasedev);
>>>> + qemu_mutex_unlock(&migration->lock);
>>>> +
>>>> + if (ret < 0) {
>>>> + error_report("vfio_save_buffer failed %s",
>>>> + strerror(errno));
>>>> + return ret;
>>>> + }
>>>> +
>>>> + qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
>>>> +
>>>> + ret = qemu_file_get_error(f);
>>>> + if (ret) {
>>>> + return ret;
>>>> + }
>>>> +
>>>> + return ret;
>>>> +}
>>>> +
>>>> +static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
>>>> +{
>>>> + VFIODevice *vbasedev = opaque;
>>>> + VFIOMigration *migration = vbasedev->migration;
>>>> + int ret;
>>>> +
>>>> + ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_SAVING);
>>>> + if (ret) {
>>>> + error_report("Failed to set state STOP and SAVING");
>>>> + return ret;
>>>> + }
>>>> +
>>>> + ret = vfio_save_device_config_state(f, opaque);
>>>> + if (ret) {
>>>> + return ret;
>>>> + }
>>>> +
>>>> + ret = vfio_update_pending(vbasedev);
>>>> + if (ret) {
>>>> + return ret;
>>>> + }
>>>> +
>>>> + while (migration->pending_bytes > 0) {
>>>> + qemu_put_be64(f, VFIO_MIG_FLAG_DEV_DATA_STATE);
>>>> + ret = vfio_save_buffer(f, vbasedev);
>>>> + if (ret < 0) {
>>>> + error_report("Failed to save buffer");
>>>> + return ret;
>>>> + } else if (ret == 0) {
>>>> + break;
>>>> + }
>>>> +
>>>> + ret = vfio_update_pending(vbasedev);
>>>> + if (ret) {
>>>> + return ret;
>>>> + }
>>>> + }
>>>> +
>>>> + qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
>>>> +
>>>> + ret = qemu_file_get_error(f);
>>>> + if (ret) {
>>>> + return ret;
>>>> + }
>>>> +
>>>> + ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOPPED);
>>>> + if (ret) {
>>>> + error_report("Failed to set state STOPPED");
>>>> + 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,
>>>> };
>>>>
>>>> /* ---------------------------------------------------------------------- */
>>>
>
next prev parent reply other threads:[~2019-06-21 19:39 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-20 14:37 [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device Kirti Wankhede
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 01/13] vfio: KABI for migration interface Kirti Wankhede
2019-06-20 17:18 ` Alex Williamson
2019-06-21 5:52 ` Kirti Wankhede
2019-06-21 15:03 ` Alex Williamson
2019-06-21 19:35 ` Kirti Wankhede
2019-06-21 20:00 ` Alex Williamson
2019-06-21 20:30 ` Kirti Wankhede
2019-06-21 22:01 ` Alex Williamson
2019-06-24 15:00 ` Kirti Wankhede
2019-06-24 15:25 ` Alex Williamson
2019-06-24 18:52 ` Kirti Wankhede
2019-06-24 19:01 ` Alex Williamson
2019-06-25 15:20 ` Kirti Wankhede
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 02/13] vfio: Add function to unmap VFIO region Kirti Wankhede
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 03/13] vfio: Add save and load functions for VFIO PCI devices Kirti Wankhede
2019-06-21 0:12 ` Yan Zhao
2019-06-21 6:44 ` Kirti Wankhede
2019-06-21 7:50 ` Yan Zhao
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 04/13] vfio: Add migration region initialization and finalize function Kirti Wankhede
2019-06-24 14:00 ` Cornelia Huck
2019-06-27 14:56 ` Kirti Wankhede
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 05/13] vfio: Add VM state change handler to know state of VM Kirti Wankhede
2019-06-25 10:29 ` Dr. David Alan Gilbert
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 06/13] vfio: Add migration state change notifier Kirti Wankhede
2019-06-27 10:33 ` Dr. David Alan Gilbert
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 07/13] vfio: Register SaveVMHandlers for VFIO device Kirti Wankhede
2019-06-27 10:01 ` Dr. David Alan Gilbert
2019-06-27 14:31 ` Kirti Wankhede
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 08/13] vfio: Add save state functions to SaveVMHandlers Kirti Wankhede
2019-06-20 19:25 ` Alex Williamson
2019-06-21 6:38 ` Kirti Wankhede
2019-06-21 15:16 ` Alex Williamson
2019-06-21 19:38 ` Kirti Wankhede [this message]
2019-06-21 20:02 ` Alex Williamson
2019-06-21 20:07 ` Kirti Wankhede
2019-06-21 20:32 ` Alex Williamson
2019-06-21 21:05 ` Kirti Wankhede
2019-06-21 22:13 ` Alex Williamson
2019-06-24 14:31 ` Kirti Wankhede
2019-06-21 0:31 ` Yan Zhao
2019-06-25 3:30 ` Yan Zhao
2019-06-28 8:50 ` Dr. David Alan Gilbert
2019-06-28 21:16 ` Yan Zhao
2019-06-28 9:09 ` Dr. David Alan Gilbert
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 09/13] vfio: Add load " Kirti Wankhede
2019-06-28 9:18 ` Dr. David Alan Gilbert
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 10/13] vfio: Add function to get dirty page list Kirti Wankhede
2019-06-26 0:40 ` Yan Zhao
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 11/13] vfio: Add vfio_listerner_log_sync to mark dirty pages Kirti Wankhede
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 12/13] vfio: Make vfio-pci device migration capable Kirti Wankhede
2019-06-20 14:37 ` [Qemu-devel] [PATCH v4 13/13] vfio: Add trace events in migration code path Kirti Wankhede
2019-06-20 18:50 ` Dr. David Alan Gilbert
2019-06-21 5:54 ` Kirti Wankhede
2019-06-21 0:25 ` [Qemu-devel] [PATCH v4 00/13] Add migration support for VFIO device Yan Zhao
2019-06-21 1:24 ` Yan Zhao
2019-06-21 8:02 ` Kirti Wankhede
2019-06-21 8:46 ` Yan Zhao
2019-06-21 9:22 ` Kirti Wankhede
2019-06-21 10:45 ` Yan Zhao
2019-06-24 19:00 ` Dr. David Alan Gilbert
2019-06-26 0:43 ` Yan Zhao
2019-06-28 9:44 ` Dr. David Alan Gilbert
2019-06-28 21:28 ` Yan Zhao
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=b345a59c-b34d-c589-be78-b7a7690e80b2@nvidia.com \
--to=kwankhede@nvidia.com \
--cc=Ken.Xue@amd.com \
--cc=Zhengxiao.zx@Alibaba-inc.com \
--cc=aik@ozlabs.ru \
--cc=alex.williamson@redhat.com \
--cc=changpeng.liu@intel.com \
--cc=cjia@nvidia.com \
--cc=cohuck@redhat.com \
--cc=dgilbert@redhat.com \
--cc=eauger@redhat.com \
--cc=eskultet@redhat.com \
--cc=felipe@nutanix.com \
--cc=jonathan.davies@nutanix.com \
--cc=kevin.tian@intel.com \
--cc=mlevitsk@redhat.com \
--cc=pasic@linux.ibm.com \
--cc=qemu-devel@nongnu.org \
--cc=shuangtai.tst@alibaba-inc.com \
--cc=yan.y.zhao@intel.com \
--cc=yi.l.liu@intel.com \
--cc=zhi.a.wang@intel.com \
--cc=ziye.yang@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).