From: Cornelia Huck <cohuck@redhat.com>
To: Kirti Wankhede <kwankhede@nvidia.com>
Cc: cjia@nvidia.com, aik@ozlabs.ru, Zhengxiao.zx@Alibaba-inc.com,
shuangtai.tst@alibaba-inc.com, qemu-devel@nongnu.org,
peterx@redhat.com, eauger@redhat.com, yi.l.liu@intel.com,
quintela@redhat.com, ziye.yang@intel.com, armbru@redhat.com,
mlevitsk@redhat.com, pasic@linux.ibm.com, felipe@nutanix.com,
zhi.a.wang@intel.com, kevin.tian@intel.com, yan.y.zhao@intel.com,
dgilbert@redhat.com, alex.williamson@redhat.com,
changpeng.liu@intel.com, eskultet@redhat.com, Ken.Xue@amd.com,
jonathan.davies@nutanix.com, pbonzini@redhat.com
Subject: Re: [PATCH v26 09/17] vfio: Add load state functions to SaveVMHandlers
Date: Tue, 20 Oct 2020 18:25:32 +0200 [thread overview]
Message-ID: <20201020182532.76b544b6.cohuck@redhat.com> (raw)
In-Reply-To: <5ca09cd6-efd6-ed8d-277f-5a1b42b5835c@nvidia.com>
On Mon, 19 Oct 2020 02:17:43 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 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.
Yes, but that's what I find confusing... a missing or incorrect
vfio_load_config callback does not have anything to do with incorrect
end flags as present in the stream, but with the consumer not reading
things correctly. If I got this error, I would go looking whether
there's anything wrong with the stream and the code that produced it,
and that's the wrong direction.
(...)
> >> +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)
Of course, but I don't find it easy to follow when the errors are
happening.
>
>
> > 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;
> }
Hm.
What I find not that easy to follow is the structure here:
while (!end_marker) {
switch (data) {
case config_state:
if (load_config)
return error;
break;
case setup_state:
read_next_value();
if (end_marker)
return 0;
else
return error;
break;
case data_state:
size = read_next_value();
if (!size)
break;
if (vfio_load_buffer())
return error;
break;
default:
return error;
}
read_next_value();
if (qemu_file_get_error())
return error;
}
So, what I don't understand is:
- Why do we call qemu_file_get_error() only after we went through the
whole switch? This means it is never called for the
setup_state/end_marker pair.
- If we look for an end marker for config_state and data_state, it's
buried in the called functions. How can we be sure they actually do
look for it? That needs at least a comment.
- If we find a valid setup_state section, we return success
immediately. If we find valid config_state or data_state sections, we
keep looking for more sections. Why? This also needs at least a
comment.
>
> 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;
> >> +}
> >> +
next prev parent reply other threads:[~2020-10-20 16:39 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 23:24 [PATCH QEMU v25 00/17] Add migration support for VFIO devices Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 01/17] vfio: Add function to unmap VFIO region Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 02/17] vfio: Add vfio_get_object callback to VFIODeviceOps Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 03/17] vfio: Add save and load functions for VFIO PCI devices Kirti Wankhede
2020-09-23 6:38 ` Zenghui Yu
2020-09-24 22:49 ` Alex Williamson
2020-10-21 9:30 ` Zenghui Yu
2020-10-21 19:03 ` Alex Williamson
2020-09-22 23:24 ` [PATCH v26 04/17] vfio: Add migration region initialization and finalize function Kirti Wankhede
2020-09-24 14:08 ` Cornelia Huck
2020-10-17 20:14 ` Kirti Wankhede
2020-09-25 20:20 ` Alex Williamson
2020-09-28 9:39 ` Cornelia Huck
2020-10-17 20:17 ` Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 05/17] vfio: Add VM state change handler to know state of VM Kirti Wankhede
2020-09-24 15:02 ` Cornelia Huck
2020-09-29 11:03 ` Dr. David Alan Gilbert
2020-10-17 20:24 ` Kirti Wankhede
2020-10-20 10:51 ` Cornelia Huck
2020-10-21 5:33 ` Kirti Wankhede
2020-10-22 7:51 ` Cornelia Huck
2020-10-22 15:42 ` Kirti Wankhede
2020-10-22 15:49 ` Cornelia Huck
2020-09-25 20:20 ` Alex Williamson
2020-10-17 20:30 ` Kirti Wankhede
2020-10-17 23:44 ` Alex Williamson
2020-10-18 17:43 ` Kirti Wankhede
2020-10-19 17:51 ` Alex Williamson
2020-10-20 10:23 ` Cornelia Huck
2020-09-22 23:24 ` [PATCH v26 06/17] vfio: Add migration state change notifier Kirti Wankhede
2020-09-25 20:20 ` Alex Williamson
2020-10-17 20:35 ` Kirti Wankhede
2020-10-19 17:57 ` Alex Williamson
2020-10-20 10:55 ` Cornelia Huck
2020-09-22 23:24 ` [PATCH v26 07/17] vfio: Register SaveVMHandlers for VFIO device Kirti Wankhede
2020-09-24 15:15 ` Philippe Mathieu-Daudé
2020-09-29 10:19 ` Dr. David Alan Gilbert
2020-10-17 20:36 ` Kirti Wankhede
2020-09-25 11:53 ` Cornelia Huck
2020-10-18 20:55 ` Kirti Wankhede
2020-10-20 15:51 ` Cornelia Huck
2020-09-25 20:20 ` Alex Williamson
2020-10-18 17:40 ` Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 08/17] vfio: Add save state functions to SaveVMHandlers Kirti Wankhede
2020-09-23 11:42 ` Wang, Zhi A
2020-10-21 14:30 ` Kirti Wankhede
2020-09-25 21:02 ` Alex Williamson
2020-10-18 18:00 ` Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 09/17] vfio: Add load " Kirti Wankhede
2020-10-01 10:07 ` Cornelia Huck
2020-10-18 20:47 ` Kirti Wankhede
2020-10-20 16:25 ` Cornelia Huck [this message]
2020-09-22 23:24 ` [PATCH v26 10/17] memory: Set DIRTY_MEMORY_MIGRATION when IOMMU is enabled Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 11/17] vfio: Get migration capability flags for container Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 12/17] vfio: Add function to start and stop dirty pages tracking Kirti Wankhede
2020-09-25 21:55 ` Alex Williamson
2020-10-18 20:52 ` Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 13/17] vfio: create mapped iova list when vIOMMU is enabled Kirti Wankhede
2020-09-25 22:23 ` Alex Williamson
2020-10-19 6:01 ` Kirti Wankhede
2020-10-19 17:24 ` Alex Williamson
2020-10-19 19:15 ` Kirti Wankhede
2020-10-19 20:07 ` Alex Williamson
2020-09-22 23:24 ` [PATCH v26 14/17] vfio: Add vfio_listener_log_sync to mark dirty pages Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 15/17] vfio: Add ioctl to get dirty pages bitmap during dma unmap Kirti Wankhede
2020-09-22 23:24 ` [PATCH v26 16/17] vfio: Make vfio-pci device migration capable Kirti Wankhede
2020-09-25 12:17 ` Cornelia Huck
2020-09-22 23:24 ` [PATCH v26 17/17] qapi: Add VFIO devices migration stats in Migration stats Kirti Wankhede
2020-09-24 15:14 ` Eric Blake
2020-09-25 22:55 ` Alex Williamson
2020-09-29 10:40 ` Dr. David Alan Gilbert
2020-09-23 7:06 ` [PATCH QEMU v25 00/17] Add migration support for VFIO devices Zenghui Yu
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=20201020182532.76b544b6.cohuck@redhat.com \
--to=cohuck@redhat.com \
--cc=Ken.Xue@amd.com \
--cc=Zhengxiao.zx@Alibaba-inc.com \
--cc=aik@ozlabs.ru \
--cc=alex.williamson@redhat.com \
--cc=armbru@redhat.com \
--cc=changpeng.liu@intel.com \
--cc=cjia@nvidia.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=kwankhede@nvidia.com \
--cc=mlevitsk@redhat.com \
--cc=pasic@linux.ibm.com \
--cc=pbonzini@redhat.com \
--cc=peterx@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=quintela@redhat.com \
--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).