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Thu, 5 Mar 2020 12:32:11 +0000 (UTC) Received: from work-vm (unknown [10.36.118.152]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E5A9873891; Thu, 5 Mar 2020 12:31:58 +0000 (UTC) Date: Thu, 5 Mar 2020 12:31:55 +0000 From: "Dr. David Alan Gilbert" To: Jagannathan Raman Subject: Re: [PATCH v5 41/50] multi-process/mig: Enable VMSD save in the Proxy object Message-ID: <20200305123155.GH3130@work-vm> References: MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 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: elena.ufimtseva@oracle.com, fam@euphon.net, swapnil.ingle@nutanix.com, john.g.johnson@oracle.com, qemu-devel@nongnu.org, kraxel@redhat.com, quintela@redhat.com, mst@redhat.com, armbru@redhat.com, kanth.ghatraju@oracle.com, felipe@nutanix.com, thuth@redhat.com, ehabkost@redhat.com, konrad.wilk@oracle.com, liran.alon@oracle.com, stefanha@redhat.com, thanos.makatos@nutanix.com, rth@twiddle.net, kwolf@redhat.com, berrange@redhat.com, mreitz@redhat.com, ross.lagerwall@citrix.com, marcandre.lureau@gmail.com, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Jagannathan Raman (jag.raman@oracle.com) wrote: > Collect the VMSD from remote process on the source and save > it to the channel leading to the destination >=20 > Signed-off-by: Elena Ufimtseva > Signed-off-by: John G Johnson > Signed-off-by: Jagannathan Raman > --- > v4 -> v5: > - Using qemu_file_shutdown() instead of qemu_thread_cancel(). Removed p= atch > which introduced qemu_thread_cancel() >=20 > hw/proxy/qemu-proxy.c | 135 ++++++++++++++++++++++++++++++++++++= ++++++ > include/hw/proxy/qemu-proxy.h | 2 + > include/io/mpqemu-link.h | 1 + > 3 files changed, 138 insertions(+) >=20 > diff --git a/hw/proxy/qemu-proxy.c b/hw/proxy/qemu-proxy.c > index b1b9282..19f0dbb 100644 > --- a/hw/proxy/qemu-proxy.c > +++ b/hw/proxy/qemu-proxy.c > @@ -23,6 +23,14 @@ > #include "util/event_notifier-posix.c" > #include "hw/boards.h" > #include "include/qemu/log.h" > +#include "io/channel.h" > +#include "migration/qemu-file-types.h" > +#include "qapi/error.h" > +#include "io/channel-util.h" > +#include "migration/qemu-file-channel.h" > +#include "migration/qemu-file.h" > +#include "migration/migration.h" > +#include "migration/vmstate.h" > =20 > QEMUTimer *hb_timer; > static void pci_proxy_dev_realize(PCIDevice *dev, Error **errp); > @@ -35,6 +43,9 @@ static void broadcast_init(void); > static int config_op_send(PCIProxyDev *dev, uint32_t addr, uint32_t *val= , int l, > unsigned int op); > =20 > +#define PAGE_SIZE qemu_real_host_page_size > +uint8_t *mig_data; > + > static void childsig_handler(int sig, siginfo_t *siginfo, void *ctx) > { > /* TODO: Add proper handler. */ > @@ -460,6 +471,129 @@ static void pci_proxy_dev_inst_init(Object *obj) > dev->mem_init =3D false; > } > =20 > +typedef struct { > + QEMUFile *rem; > + PCIProxyDev *dev; > +} proxy_mig_data; > + > +static void *proxy_mig_out(void *opaque) > +{ > + proxy_mig_data *data =3D opaque; > + PCIProxyDev *dev =3D data->dev; > + uint8_t byte; > + uint64_t data_size =3D PAGE_SIZE; > + > + mig_data =3D g_malloc(data_size); > + > + while (true) { > + byte =3D qemu_get_byte(data->rem); > + > + if (qemu_file_get_error(data->rem)) { > + break; > + } > + > + mig_data[dev->migsize++] =3D byte; > + if (dev->migsize =3D=3D data_size) { > + data_size +=3D PAGE_SIZE; > + mig_data =3D g_realloc(mig_data, data_size); > + } > + } > + > + return NULL; > +} > + > +static int proxy_pre_save(void *opaque) > +{ > + PCIProxyDev *pdev =3D opaque; > + proxy_mig_data *mig_data; > + QEMUFile *f_remote; > + MPQemuMsg msg =3D {0}; > + QemuThread thread; > + Error *err =3D NULL; > + QIOChannel *ioc; > + uint64_t size; > + int fd[2]; > + > + if (socketpair(AF_UNIX, SOCK_STREAM, 0, fd)) { > + return -1; > + } > + > + ioc =3D qio_channel_new_fd(fd[0], &err); > + if (err) { > + error_report_err(err); > + return -1; > + } > + > + qio_channel_set_name(QIO_CHANNEL(ioc), "PCIProxyDevice-mig"); > + > + f_remote =3D qemu_fopen_channel_input(ioc); > + > + pdev->migsize =3D 0; > + > + mig_data =3D g_malloc0(sizeof(proxy_mig_data)); > + mig_data->rem =3D f_remote; This feels way too complicated. Since we know f_remote is always just a simple fd we're getting we don't need to use qio or qemu_file here; just use the fd - nice and simple. Then the code to read it can just use read(2) with a sensible size chunk rather than reading a byte at a time. > + mig_data->dev =3D pdev; > + > + qemu_thread_create(&thread, "Proxy MIG_OUT", proxy_mig_out, mig_data= , > + QEMU_THREAD_DETACHED); I'm just checking why a thread is necessary; is this because you need to be able to start reading before you block waiting for the remote to tell you the size - worrying that if you don't start reading then the remote might block waiting for us? > + msg.cmd =3D START_MIG_OUT; > + msg.bytestream =3D 0; > + msg.num_fds =3D 2; > + msg.fds[0] =3D fd[1]; > + msg.fds[1] =3D GET_REMOTE_WAIT; > + > + mpqemu_msg_send(&msg, pdev->mpqemu_link->com); > + size =3D wait_for_remote(msg.fds[1]); > + PUT_REMOTE_WAIT(msg.fds[1]); > + > + assert(size !=3D ULLONG_MAX); > + > + /* > + * migsize is being update by a separate thread. Using volatile to > + * instruct the compiler to fetch the value of this variable from > + * memory during every read > + */ > + while (*((volatile uint64_t *)&pdev->migsize) < size) { > + } Hmm. I suggest the following: a) You create a shared 'size' variable; and initialize it to UINT64_MAX. b) The thread uses atomic_read(shared_size) to read that value. c) When you receive the size from the remote you do atomic_set(&shared_size, size); d) The thread does: while (received_size < atomic_read(&shared_size)) so the thread will quit either on EOF or it hitting the size. e) We pthread_join here to wait for the thread f) We then check a received size to make sure it matches what we expect. That removes the tight loop. > + qemu_file_shutdown(f_remote); > + > + qemu_fclose(f_remote); > + close(fd[1]); > + > + return 0; > +} > + > +static int proxy_post_save(void *opaque) > +{ > + MigrationState *ms =3D migrate_get_current(); > + PCIProxyDev *pdev =3D opaque; > + uint64_t pos =3D 0; > + > + while (pos < pdev->migsize) { > + qemu_put_byte(ms->to_dst_file, mig_data[pos]); > + pos++; > + } > + > + qemu_fflush(ms->to_dst_file); > + > + return 0; I don't think you need that. > +} > + > +const VMStateDescription vmstate_pci_proxy_device =3D { > + .name =3D "PCIProxyDevice", > + .version_id =3D 2, > + .minimum_version_id =3D 1, > + .pre_save =3D proxy_pre_save, > + .post_save =3D proxy_post_save, > + .fields =3D (VMStateField[]) { > + VMSTATE_PCI_DEVICE(parent_dev, PCIProxyDev), > + VMSTATE_UINT64(migsize, PCIProxyDev), I think instead you should use a VMSTATE_VBUFFER here to save the mig_data. What we should do is the post_save should g_free the buffer. (mig_data should be a field in proxy). Dave > + VMSTATE_END_OF_LIST() > + } > +}; > + > static void pci_proxy_dev_class_init(ObjectClass *klass, void *data) > { > PCIDeviceClass *k =3D PCI_DEVICE_CLASS(klass); > @@ -471,6 +605,7 @@ static void pci_proxy_dev_class_init(ObjectClass *kla= ss, void *data) > k->config_write =3D pci_proxy_write_config; > =20 > dc->reset =3D proxy_device_reset; > + dc->vmsd =3D &vmstate_pci_proxy_device; > } > =20 > static const TypeInfo pci_proxy_dev_type_info =3D { > diff --git a/include/hw/proxy/qemu-proxy.h b/include/hw/proxy/qemu-proxy.= h > index 5de8129..537c227 100644 > --- a/include/hw/proxy/qemu-proxy.h > +++ b/include/hw/proxy/qemu-proxy.h > @@ -75,6 +75,8 @@ struct PCIProxyDev { > bool need_spawn, Error **errp); > =20 > ProxyMemoryRegion region[PCI_NUM_REGIONS]; > + > + uint64_t migsize; > }; > =20 > typedef struct PCIProxyDevClass { > diff --git a/include/io/mpqemu-link.h b/include/io/mpqemu-link.h > index d2234ca..b42c003 100644 > --- a/include/io/mpqemu-link.h > +++ b/include/io/mpqemu-link.h > @@ -63,6 +63,7 @@ typedef enum { > PROXY_PING, > MMIO_RETURN, > DEVICE_RESET, > + START_MIG_OUT, > MAX, > } mpqemu_cmd_t; > =20 > --=20 > 1.8.3.1 >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK