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Thu, 20 Jun 2019 23:38:44 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 20 Jun 2019 23:38:42 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 20 Jun 2019 23:38:42 -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 06:38:32 +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> X-Nvconfidentiality: public From: Kirti Wankhede Message-ID: <9256515a-f815-58e1-c9ca-81d64bac6db1@nvidia.com> Date: Fri, 21 Jun 2019 12:08:26 +0530 MIME-Version: 1.0 In-Reply-To: <20190620132505.1cf64ac5@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=1561099124; bh=Eexj3FijL5GRfasXvd/K2eVD0H6Q5w3bzGmMbqGkbx4=; 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=m5PgaNpBD9rqM3FTeB7HaFl23k+6V0q/vOfhdggKWcIkpGsl5uM2jz0VPHI3vBGFW PXrQkRu2xhX23mqJtaH9cSWPjLlZMbqJNmRso9N5wiL2fF5Z3/fHLVODRHrr6gzwq6 etzf0MReNuWwFbTd/Qal1DByj87WAqr3g3YFpFBn0Tk4DXoEn+slgneWYIwfdm/fuh hZ3R7cB0/dZQnbnkTbM8l7Ee8hpFwONDyI/4vXo6bETjeFagILxs204LBwlOwgpxSg wJryZqxUBkRQg/Hhrq+ToRTCwW+F8v5qklIuE2BmJ1oji/ACHUb9vXZjhhXaJQZWQD EJCNv6+TMKNgg== 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, yulei.zhang@intel.com, 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 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. > 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. > >> + 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, >> }; >> >> /* ---------------------------------------------------------------------- */ >