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From: Yan Zhao <yan.y.zhao@intel.com>
To: Kirti Wankhede <kwankhede@nvidia.com>
Cc: "Zhengxiao.zx@Alibaba-inc.com" <Zhengxiao.zx@Alibaba-inc.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	"Liu, Yi L" <yi.l.liu@intel.com>,
	"cjia@nvidia.com" <cjia@nvidia.com>,
	"eskultet@redhat.com" <eskultet@redhat.com>,
	"Yang, Ziye" <ziye.yang@intel.com>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	"cohuck@redhat.com" <cohuck@redhat.com>,
	"shuangtai.tst@alibaba-inc.com" <shuangtai.tst@alibaba-inc.com>,
	"dgilbert@redhat.com" <dgilbert@redhat.com>,
	"Wang, Zhi A" <zhi.a.wang@intel.com>,
	"mlevitsk@redhat.com" <mlevitsk@redhat.com>,
	"pasic@linux.ibm.com" <pasic@linux.ibm.com>,
	"aik@ozlabs.ru" <aik@ozlabs.ru>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"eauger@redhat.com" <eauger@redhat.com>,
	"felipe@nutanix.com" <felipe@nutanix.com>,
	"jonathan.davies@nutanix.com" <jonathan.davies@nutanix.com>,
	"Liu, Changpeng" <changpeng.liu@intel.com>,
	"Ken.Xue@amd.com" <Ken.Xue@amd.com>
Subject: Re: [PATCH v16 QEMU 09/16] vfio: Add save state functions to SaveVMHandlers
Date: Mon, 11 May 2020 20:50:33 -0400
Message-ID: <20200512005033.GA27524@joy-OptiPlex-7040> (raw)
In-Reply-To: <7653e660-1360-7c2b-c4c7-3b53081f14e3@nvidia.com>

On Mon, May 11, 2020 at 06:22:47PM +0800, Kirti Wankhede wrote:
> 
> 
> On 5/9/2020 11:01 AM, Yan Zhao wrote:
> > On Wed, Mar 25, 2020 at 05:09:07AM +0800, Kirti Wankhede 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. If pending_bytes > 0, go through below steps.
> >> - read data_offset - indicates kernel driver to write data to staging
> >>    buffer.
> >> - read data_size - amount of data in bytes written by vendor driver in
> >>    migration region.
> > I think we should change the sequence of reading data_size and
> > data_offset. see the next comment below.
> > 
> >> - read data_size bytes of data from data_offset in the migration region.
> >> - 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. If pending_bytes > 0, go through below steps.
> >> c. read data_offset - indicates kernel driver to write data to staging
> >>     buffer.
> >> d. read data_size - amount of data in bytes written by vendor driver in
> >>     migration region.
> >> e. read data_size bytes of data from data_offset in the migration region.
> >> f. Write data packet as below:
> >>     {VFIO_MIG_FLAG_DEV_DATA_STATE, data_size, actual data}
> >> g. iterate through steps b to f while (pending_bytes > 0)
> >> h. Write {VFIO_MIG_FLAG_END_OF_STATE}
> >>
> >> When data region is mapped, its user's responsibility to read data from
> >> data_offset of data_size before moving to next steps.
> >>
> >> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> >> Reviewed-by: Neo Jia <cjia@nvidia.com>
> >> ---
> >>   hw/vfio/migration.c           | 245 +++++++++++++++++++++++++++++++++++++++++-
> >>   hw/vfio/trace-events          |   6 ++
> >>   include/hw/vfio/vfio-common.h |   1 +
> >>   3 files changed, 251 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> >> index 033f76526e49..ecbeed5182c2 100644
> >> --- a/hw/vfio/migration.c
> >> +++ b/hw/vfio/migration.c
> >> @@ -138,6 +138,137 @@ static int vfio_migration_set_state(VFIODevice *vbasedev, uint32_t mask,
> >>       return 0;
> >>   }
> >>   
> >> +static void *find_data_region(VFIORegion *region,
> >> +                              uint64_t data_offset,
> >> +                              uint64_t data_size)
> >> +{
> >> +    void *ptr = NULL;
> >> +    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) &&
> >> +            (data_size <= region->mmaps[i].size)) {
> >> +            ptr = region->mmaps[i].mmap + (data_offset -
> >> +                                           region->mmaps[i].offset);
> >> +            break;
> >> +        }
> >> +    }
> >> +    return ptr;
> >> +}
> >> +
> >> +static int vfio_save_buffer(QEMUFile *f, VFIODevice *vbasedev)
> >> +{
> >> +    VFIOMigration *migration = vbasedev->migration;
> >> +    VFIORegion *region = &migration->region;
> >> +    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("%s: Failed to get migration buffer data offset %d",
> >> +                     vbasedev->name, 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("%s: Failed to get migration buffer data size %d",
> >> +                     vbasedev->name, ret);
> >> +        return -EINVAL;
> >> +    }
> > data_size should be read first, and if it's 0, data_offset will not
> > be read further.
> > 
> > the reasons are below:
> > 1. if there's no data region provided by vendor driver, there's no
> > reason to get a valid data_offset, so reading/writing of data_offset
> > should fail. And this should not be treated as a migration error.
> > 
> > 2. even if pending_bytes is 0, vfio_save_iterate() is still possible to be
> > called and therefore vfio_save_buffer() is called.
> > 
> 
> As I mentioned in reply to Alex in:
> https://lists.nongnu.org/archive/html/qemu-devel/2020-05/msg02476.html
> 
> With that, vfio_save_iterate() will read pending_bytes if its 0 and then 
> if pending_bytes is not 0 then call vfio_save_buffer(). With that your 
> above concerns should get resolved.
>
what if pending_bytes is not 0, but vendor driver just does not want to
send data in this iteration? isn't it right to get data_size first before
getting data_offset?

Thanks
Yan


  reply index

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24 21:08 [PATCH v16 QEMU 00/16] Add migration support for VFIO devices Kirti Wankhede
2020-03-24 21:08 ` [PATCH v16 QEMU 01/16] vfio: KABI for migration interface - Kernel header placeholder Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 02/16] vfio: Add function to unmap VFIO region Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 03/16] vfio: Add vfio_get_object callback to VFIODeviceOps Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 04/16] vfio: Add save and load functions for VFIO PCI devices Kirti Wankhede
2020-03-25 19:56   ` Alex Williamson
2020-03-26 17:29     ` Dr. David Alan Gilbert
2020-03-26 17:38       ` Alex Williamson
2020-05-04 23:18     ` Kirti Wankhede
2020-05-05  4:37       ` Alex Williamson
2020-05-06  6:11         ` Yan Zhao
2020-05-06 19:48           ` Kirti Wankhede
2020-05-06 20:03             ` Alex Williamson
2020-05-07  5:40               ` Kirti Wankhede
2020-05-07 18:14                 ` Alex Williamson
2020-03-26 17:46   ` Dr. David Alan Gilbert
2020-05-04 23:19     ` Kirti Wankhede
2020-04-07  4:10   ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2020-05-04 23:21     ` Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 05/16] vfio: Add migration region initialization and finalize function Kirti Wankhede
2020-03-26 17:52   ` Dr. David Alan Gilbert
2020-05-04 23:19     ` Kirti Wankhede
2020-05-19 19:32       ` Dr. David Alan Gilbert
2020-03-24 21:09 ` [PATCH v16 QEMU 06/16] vfio: Add VM state change handler to know state of VM Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 07/16] vfio: Add migration state change notifier Kirti Wankhede
2020-04-01 11:27   ` Dr. David Alan Gilbert
2020-05-04 23:20     ` Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 08/16] vfio: Register SaveVMHandlers for VFIO device Kirti Wankhede
2020-03-25 21:02   ` Alex Williamson
2020-05-04 23:19     ` Kirti Wankhede
2020-05-05  4:37       ` Alex Williamson
2020-05-06  6:38         ` Yan Zhao
2020-05-06  9:58           ` Cornelia Huck
2020-05-06 16:53             ` Dr. David Alan Gilbert
2020-05-06 19:30               ` Kirti Wankhede
2020-05-07  6:37                 ` Cornelia Huck
2020-05-07 20:29                 ` Alex Williamson
2020-04-01 17:36   ` Dr. David Alan Gilbert
2020-05-04 23:20     ` Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 09/16] vfio: Add save state functions to SaveVMHandlers Kirti Wankhede
2020-03-25 22:03   ` Alex Williamson
2020-05-04 23:18     ` Kirti Wankhede
2020-05-05  4:37       ` Alex Williamson
2020-05-11  9:53         ` Kirti Wankhede
2020-05-11 15:59           ` Alex Williamson
2020-05-12  2:06           ` Yan Zhao
2020-05-09  5:31   ` Yan Zhao
2020-05-11 10:22     ` Kirti Wankhede
2020-05-12  0:50       ` Yan Zhao [this message]
2020-03-24 21:09 ` [PATCH v16 QEMU 10/16] vfio: Add load " Kirti Wankhede
2020-03-25 22:36   ` Alex Williamson
2020-04-01 18:58   ` Dr. David Alan Gilbert
2020-05-04 23:20     ` Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 11/16] iommu: add callback to get address limit IOMMU supports Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 12/16] memory: Set DIRTY_MEMORY_MIGRATION when IOMMU is enabled Kirti Wankhede
2020-04-01 19:00   ` Dr. David Alan Gilbert
2020-04-01 19:42     ` Alex Williamson
2020-03-24 21:09 ` [PATCH v16 QEMU 13/16] vfio: Add function to start and stop dirty pages tracking Kirti Wankhede
2020-03-26 19:10   ` Alex Williamson
2020-05-04 23:20     ` Kirti Wankhede
2020-04-01 19:03   ` Dr. David Alan Gilbert
2020-05-04 23:21     ` Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 14/16] vfio: Add vfio_listener_log_sync to mark dirty pages Kirti Wankhede
2020-03-25  2:19   ` Yan Zhao
2020-03-26 19:46   ` Alex Williamson
2020-04-01 19:08     ` Dr. David Alan Gilbert
2020-04-01  5:50   ` Yan Zhao
2020-04-03 20:11     ` Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 15/16] vfio: Add ioctl to get dirty pages bitmap during dma unmap Kirti Wankhede
2020-03-24 21:09 ` [PATCH v16 QEMU 16/16] vfio: Make vfio-pci device migration capable Kirti Wankhede
2020-03-24 23:36 ` [PATCH v16 QEMU 00/16] Add migration support for VFIO devices no-reply
2020-03-31 18:34 ` Alex Williamson
2020-04-01  6:41   ` Yan Zhao
2020-04-01 18:34     ` Alex Williamson

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