On Fri, 21 Jun 2019 12:08:26 +0530 Kirti Wankhede <kwankh...@nvidia.com> wrote:
> On 6/21/2019 12:55 AM, Alex Williamson wrote: > > On Thu, 20 Jun 2019 20:07:36 +0530 > > Kirti Wankhede <kwankh...@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 <kwankh...@nvidia.com> > >> Reviewed-by: Neo Jia <c...@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? 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, > >> }; > >> > >> /* ---------------------------------------------------------------------- > >> */ > >