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Fri, 21 Jun 2019 12:38:57 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Fri, 21 Jun 2019 12:38:55 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Fri, 21 Jun 2019 12:38:55 -0700 Received: from [10.24.71.210] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 21 Jun 2019 19:38:45 +0000 To: Alex Williamson References: <1561041461-22326-1-git-send-email-kwankhede@nvidia.com> <1561041461-22326-9-git-send-email-kwankhede@nvidia.com> <20190620132505.1cf64ac5@x1.home> <9256515a-f815-58e1-c9ca-81d64bac6db1@nvidia.com> <20190621091638.18127e7a@x1.home> X-Nvconfidentiality: public From: Kirti Wankhede Message-ID: Date: Sat, 22 Jun 2019 01:08:40 +0530 MIME-Version: 1.0 In-Reply-To: <20190621091638.18127e7a@x1.home> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL108.nvidia.com (172.18.146.13) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1561145937; bh=jZJWXD1NPWaSrJaO4igyig1LQLj++x3MoZucKBoe4QA=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=TZJMM2liRBBaG/nZOq+gpF5gUI/msle7C310+tA6NGVd+n15Lum2I4vLPt/v9qYOL FmM4psERNRQPKYg75zy7Za5+5Uc89z+26JmVki88TTUvqAMOBcHlbGJRqczgAEUGP9 YMGqyLh1Z7FF9mTYXWEt99I52/iKhJqL6ej7T6Q5NjbizTqRtWkV+OEwUmCV6YXVMO opIbhyGmu5C663bZLKqZKwTth6TLqijfJVh/C2qGjbrSqmWleUVTiRhjV2mFNFFy/R Cd9INvh0XHvcpjaRkH+qCHWKxkEb2yDkEyKFS16fuiub0HF74GlqOSme++L98QpIIo jKyRoYMGL11TA== X-detected-operating-system: by eggs.gnu.org: Windows 7 or 8 X-Received-From: 216.228.121.64 Subject: Re: [Qemu-devel] [PATCH v4 08/13] vfio: Add save state functions to SaveVMHandlers X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/21/2019 8:46 PM, Alex Williamson wrote: > On Fri, 21 Jun 2019 12:08:26 +0530 > Kirti Wankhede wrote: > >> On 6/21/2019 12:55 AM, Alex Williamson wrote: >>> On Thu, 20 Jun 2019 20:07:36 +0530 >>> 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 >>>> - 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 >>>> Reviewed-by: Neo Jia >>>> --- >>>> 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, >>>> }; >>>> >>>> /* ---------------------------------------------------------------------- */ >>> >