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Fri, 26 Jun 2020 14:22:45 +0000 (UTC) Date: Fri, 26 Jun 2020 15:22:43 +0100 From: "Dr. David Alan Gilbert" To: Alex Williamson Subject: Re: [PATCH QEMU v25 07/17] vfio: Register SaveVMHandlers for VFIO device Message-ID: <20200626142243.GJ3087@work-vm> References: <1592684486-18511-1-git-send-email-kwankhede@nvidia.com> <1592684486-18511-8-git-send-email-kwankhede@nvidia.com> <20200622165024.5b2eb251@x1.home> <542ced5e-0380-19b9-91d2-5f40c5857719@nvidia.com> <20200623135056.0c4957a3@x1.home> MIME-Version: 1.0 In-Reply-To: <20200623135056.0c4957a3@x1.home> User-Agent: Mutt/1.14.3 (2020-06-14) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.120; envelope-from=dgilbert@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/26 01:55:55 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action 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: cohuck@redhat.com, cjia@nvidia.com, aik@ozlabs.ru, Zhengxiao.zx@alibaba-inc.com, shuangtai.tst@alibaba-inc.com, qemu-devel@nongnu.org, peterx@redhat.com, Kirti Wankhede , 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, changpeng.liu@intel.com, eskultet@redhat.com, Ken.Xue@amd.com, jonathan.davies@nutanix.com, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Alex Williamson (alex.williamson@redhat.com) wrote: > On Wed, 24 Jun 2020 00:51:06 +0530 > Kirti Wankhede wrote: > > > On 6/23/2020 4:20 AM, Alex Williamson wrote: > > > On Sun, 21 Jun 2020 01:51:16 +0530 > > > Kirti Wankhede wrote: > > > > > >> Define flags to be used as delimeter in migration file stream. > > >> Added .save_setup and .save_cleanup functions. Mapped & unmapped migration > > >> region from these functions at source during saving or pre-copy phase. > > >> Set VFIO device state depending on VM's state. During live migration, VM is > > >> running when .save_setup is called, _SAVING | _RUNNING state is set for VFIO > > >> device. During save-restore, VM is paused, _SAVING state is set for VFIO device. > > >> > > >> Signed-off-by: Kirti Wankhede > > >> Reviewed-by: Neo Jia > > >> --- > > >> hw/vfio/migration.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > > >> hw/vfio/trace-events | 2 ++ > > >> 2 files changed, 94 insertions(+) > > >> > > >> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c > > >> index e30bd8768701..133bb5b1b3b2 100644 > > >> --- a/hw/vfio/migration.c > > >> +++ b/hw/vfio/migration.c > > >> @@ -8,12 +8,15 @@ > > >> */ > > >> > > >> #include "qemu/osdep.h" > > >> +#include "qemu/main-loop.h" > > >> +#include "qemu/cutils.h" > > >> #include > > >> > > >> #include "sysemu/runstate.h" > > >> #include "hw/vfio/vfio-common.h" > > >> #include "cpu.h" > > >> #include "migration/migration.h" > > >> +#include "migration/vmstate.h" > > >> #include "migration/qemu-file.h" > > >> #include "migration/register.h" > > >> #include "migration/blocker.h" > > >> @@ -24,6 +27,17 @@ > > >> #include "pci.h" > > >> #include "trace.h" > > >> > > >> +/* > > >> + * Flags used as delimiter: > > >> + * 0xffffffff => MSB 32-bit all 1s > > >> + * 0xef10 => emulated (virtual) function IO > > >> + * 0x0000 => 16-bits reserved for flags > > >> + */ > > >> +#define VFIO_MIG_FLAG_END_OF_STATE (0xffffffffef100001ULL) > > >> +#define VFIO_MIG_FLAG_DEV_CONFIG_STATE (0xffffffffef100002ULL) > > >> +#define VFIO_MIG_FLAG_DEV_SETUP_STATE (0xffffffffef100003ULL) > > >> +#define VFIO_MIG_FLAG_DEV_DATA_STATE (0xffffffffef100004ULL) > > >> + > > >> static void vfio_migration_region_exit(VFIODevice *vbasedev) > > >> { > > >> VFIOMigration *migration = vbasedev->migration; > > >> @@ -126,6 +140,65 @@ static int vfio_migration_set_state(VFIODevice *vbasedev, uint32_t mask, > > >> return 0; > > >> } > > >> > > >> +/* ---------------------------------------------------------------------- */ > > >> + > > >> +static int vfio_save_setup(QEMUFile *f, void *opaque) > > >> +{ > > >> + VFIODevice *vbasedev = opaque; > > >> + VFIOMigration *migration = vbasedev->migration; > > >> + int ret; > > >> + > > >> + trace_vfio_save_setup(vbasedev->name); > > >> + > > >> + qemu_put_be64(f, VFIO_MIG_FLAG_DEV_SETUP_STATE); > > >> + > > >> + if (migration->region.mmaps) { > > >> + qemu_mutex_lock_iothread(); > > >> + ret = vfio_region_mmap(&migration->region); > > >> + qemu_mutex_unlock_iothread(); > > >> + if (ret) { > > >> + error_report("%s: Failed to mmap VFIO migration region %d: %s", > > >> + vbasedev->name, migration->region.nr, > > >> + strerror(-ret)); > > >> + return ret; > > > > > > OTOH to my previous comments, this shouldn't be fatal, right? mmaps > > > are optional anyway so it should be sufficient to push an error report > > > to explain why this might be slower than normal, but we can still > > > proceed. > > > > > > > Right, defining region to be sparse mmap is optional. > > migration->region.mmaps is set if vendor driver defines sparse mmapable > > regions and VFIO_REGION_INFO_FLAG_MMAP flag is set. If this flag is set > > then error on mmap() should be fatal. > > > > If there is not mmapable region, then migration will proceed. > > It's both optional for the vendor to define sparse mmap support (or any > mmap support) and optional for the user to make use of it. The user > can recover from an mmap failure by using read/write accesses. The > vendor MUST support this. It doesn't make sense to worry about > aborting the VM in replying to comments for 05/17, where it's not clear > how we proceed, yet intentionally cause a fatal error here when there > is a very clear path to proceed. > > > >> + } > > >> + } > > >> + > > >> + ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_MASK, > > >> + VFIO_DEVICE_STATE_SAVING); > > >> + if (ret) { > > >> + error_report("%s: Failed to set state SAVING", vbasedev->name); > > >> + return ret; > > >> + } > > > > > > We seem to be lacking support in the callers for detecting if the > > > device is in an error state. I'm not sure what our options are > > > though, maybe only a hw_error(). > > > > > > > Returning error here fails migration process. And if device is in error > > state, any application running inside VM using this device would fail. > > I think, there is no need to take any special action here by detecting > > device error state. > > If QEMU knows a device has failed, it seems like it would make sense to > stop the VM, otherwise we risk an essentially endless assortment of > ways that the user might notice the guest isn't behaving normally, some > maybe even causing the user to lose data. Thanks, With GPUs especially though we can get into messy states where only the GPU is toast; for example you might get this if your GUI starts/exits/crashes during a migration - that's a bit too common to kill a VM that might have useful data on it. Dave > Alex > > > >> + > > >> + qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE); > > >> + > > >> + ret = qemu_file_get_error(f); > > >> + if (ret) { > > >> + return ret; > > >> + } > > >> + > > >> + return 0; > > >> +} > > >> + > > >> +static void vfio_save_cleanup(void *opaque) > > >> +{ > > >> + VFIODevice *vbasedev = opaque; > > >> + VFIOMigration *migration = vbasedev->migration; > > >> + > > >> + if (migration->region.mmaps) { > > >> + vfio_region_unmap(&migration->region); > > >> + } > > >> + trace_vfio_save_cleanup(vbasedev->name); > > >> +} > > >> + > > >> +static SaveVMHandlers savevm_vfio_handlers = { > > >> + .save_setup = vfio_save_setup, > > >> + .save_cleanup = vfio_save_cleanup, > > >> +}; > > >> + > > >> +/* ---------------------------------------------------------------------- */ > > >> + > > >> static void vfio_vmstate_change(void *opaque, int running, RunState state) > > >> { > > >> VFIODevice *vbasedev = opaque; > > >> @@ -180,6 +253,7 @@ static int vfio_migration_init(VFIODevice *vbasedev, > > >> struct vfio_region_info *info) > > >> { > > >> int ret; > > >> + char id[256] = ""; > > >> > > >> vbasedev->migration = g_new0(VFIOMigration, 1); > > >> > > >> @@ -192,6 +266,24 @@ static int vfio_migration_init(VFIODevice *vbasedev, > > >> return ret; > > >> } > > >> > > >> + if (vbasedev->ops->vfio_get_object) { > > > > > > Nit, vfio_migration_region_init() would have failed already if this were > > > not available. Perhaps do the test once at the start of this function > > > instead? Thanks, > > > > > > > Ok, will do that. > > > > Thanks, > > Kirti > > > > > > > Alex > > > > > >> + Object *obj = vbasedev->ops->vfio_get_object(vbasedev); > > >> + > > >> + if (obj) { > > >> + DeviceState *dev = DEVICE(obj); > > >> + char *oid = vmstate_if_get_id(VMSTATE_IF(dev)); > > >> + > > >> + if (oid) { > > >> + pstrcpy(id, sizeof(id), oid); > > >> + pstrcat(id, sizeof(id), "/"); > > >> + g_free(oid); > > >> + } > > >> + } > > >> + } > > >> + pstrcat(id, sizeof(id), "vfio"); > > >> + > > >> + register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1, &savevm_vfio_handlers, > > >> + vbasedev); > > >> vbasedev->vm_state = qemu_add_vm_change_state_handler(vfio_vmstate_change, > > >> vbasedev); > > >> vbasedev->migration_state.notify = vfio_migration_state_notifier; > > >> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events > > >> index bd3d47b005cb..86c18def016e 100644 > > >> --- a/hw/vfio/trace-events > > >> +++ b/hw/vfio/trace-events > > >> @@ -149,3 +149,5 @@ vfio_migration_probe(const char *name, uint32_t index) " (%s) Region %d" > > >> vfio_migration_set_state(const char *name, uint32_t state) " (%s) state %d" > > >> vfio_vmstate_change(const char *name, int running, const char *reason, uint32_t dev_state) " (%s) running %d reason %s device state %d" > > >> vfio_migration_state_notifier(const char *name, const char *state) " (%s) state %s" > > >> +vfio_save_setup(const char *name) " (%s)" > > >> +vfio_save_cleanup(const char *name) " (%s)" > > > > > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK