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Wed, 11 Aug 2021 23:45:26 -0700 (PDT) X-Google-Smtp-Source: ABdhPJz228XOXW20dkfgkgKkbJNhQ2X6+dDWJ75S2bkvylE9YR/0AyLC+3OIRPNFU9Jkl4aKoaP8AKSneiJnAWVPalw= X-Received: by 2002:a19:f719:: with SMTP id z25mr1446622lfe.339.1628750725845; Wed, 11 Aug 2021 23:45:25 -0700 (PDT) MIME-Version: 1.0 References: <20210811163211.185870-1-eperezma@redhat.com> In-Reply-To: From: Jason Wang Date: Thu, 12 Aug 2021 14:45:14 +0800 Message-ID: Subject: Re: [PATCH v2] vhost-vdpa: Do not send empty IOTLB update batches To: Eugenio Perez Martin Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.133.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.7, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: Eli Cohen , qemu-devel , Cindy Lu , "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Aug 12, 2021 at 2:43 PM Eugenio Perez Martin wrote: > > On Thu, Aug 12, 2021 at 8:16 AM Jason Wang wrote: > > > > On Thu, Aug 12, 2021 at 12:32 AM Eugenio P=C3=A9rez wrote: > > > > > > With the introduction of the batch hinting, meaningless batches can b= e > > > created with no IOTLB updates if the memory region was skipped by > > > vhost_vdpa_listener_skipped_section. This is the case of host notifie= rs > > > memory regions, device un/realize, and others. This causes the vdpa > > > device to receive dma mapping settings with no changes, a possibly > > > expensive operation for nothing. > > > > > > To avoid that, VHOST_IOTLB_BATCH_BEGIN hint is delayed until we have = a > > > meaningful (not skipped section) mapping or unmapping operation, and > > > VHOST_IOTLB_BATCH_END is not written unless at least one of _UPDATE / > > > _INVALIDATE has been issued. > > > > > > Signed-off-by: Eugenio P=C3=A9rez > > > --- > > > include/hw/virtio/vhost-vdpa.h | 1 + > > > hw/virtio/vhost-vdpa.c | 50 ++++++++++++++++++++++++++------= -- > > > 2 files changed, 39 insertions(+), 12 deletions(-) > > > > > > diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost= -vdpa.h > > > index e98e327f12..6538572a6f 100644 > > > --- a/include/hw/virtio/vhost-vdpa.h > > > +++ b/include/hw/virtio/vhost-vdpa.h > > > @@ -23,6 +23,7 @@ typedef struct vhost_vdpa { > > > int device_fd; > > > int index; > > > uint32_t msg_type; > > > + size_t n_mr_updated; > > > MemoryListener listener; > > > struct vhost_dev *dev; > > > VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX]; > > > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c > > > index 6ce94a1f4d..512fa18d68 100644 > > > --- a/hw/virtio/vhost-vdpa.c > > > +++ b/hw/virtio/vhost-vdpa.c > > > @@ -89,19 +89,13 @@ static int vhost_vdpa_dma_unmap(struct vhost_vdpa= *v, hwaddr iova, > > > return ret; > > > } > > > > > > -static void vhost_vdpa_listener_begin(MemoryListener *listener) > > > +static void vhost_vdpa_listener_begin_batch(struct vhost_vdpa *v) > > > { > > > - struct vhost_vdpa *v =3D container_of(listener, struct vhost_vdp= a, listener); > > > - struct vhost_dev *dev =3D v->dev; > > > - struct vhost_msg_v2 msg =3D {}; > > > int fd =3D v->device_fd; > > > - > > > - if (!(dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)= )) { > > > - return; > > > - } > > > - > > > - msg.type =3D v->msg_type; > > > - msg.iotlb.type =3D VHOST_IOTLB_BATCH_BEGIN; > > > + struct vhost_msg_v2 msg =3D { > > > + .type =3D v->msg_type, > > > + .iotlb.type =3D VHOST_IOTLB_BATCH_BEGIN, > > > + }; > > > > > > if (write(fd, &msg, sizeof(msg)) !=3D sizeof(msg)) { > > > error_report("failed to write, fd=3D%d, errno=3D%d (%s)", > > > @@ -109,6 +103,25 @@ static void vhost_vdpa_listener_begin(MemoryList= ener *listener) > > > } > > > } > > > > > > +static bool vhost_vdpa_iotlb_batch_is_started(const struct vhost_vdp= a *v) > > > +{ > > > + return v->n_mr_updated !=3D 0; > > > +} > > > + > > > +static void vhost_vdpa_iotlb_batch_begin_once(struct vhost_vdpa *v) > > > +{ > > > + if (!vhost_vdpa_iotlb_batch_is_started(v)) { > > > + vhost_vdpa_listener_begin_batch(v); > > > + } > > > + > > > + v->n_mr_updated++; > > > +} > > > + > > > +static void vhost_vdpa_iotlb_batch_reset(struct vhost_vdpa *v) > > > +{ > > > + v->n_mr_updated =3D 0; > > > +} > > > + > > > static void vhost_vdpa_listener_commit(MemoryListener *listener) > > > { > > > struct vhost_vdpa *v =3D container_of(listener, struct vhost_vdp= a, listener); > > > @@ -120,6 +133,10 @@ static void vhost_vdpa_listener_commit(MemoryLis= tener *listener) > > > return; > > > } > > > > > > + if (vhost_vdpa_iotlb_batch_is_started(v)) { > > > + return; > > > + } > > > + > > > msg.type =3D v->msg_type; > > > msg.iotlb.type =3D VHOST_IOTLB_BATCH_END; > > > > > > @@ -127,6 +144,8 @@ static void vhost_vdpa_listener_commit(MemoryList= ener *listener) > > > error_report("failed to write, fd=3D%d, errno=3D%d (%s)", > > > fd, errno, strerror(errno)); > > > } > > > + > > > + vhost_vdpa_iotlb_batch_reset(v); > > > } > > > > > > static void vhost_vdpa_listener_region_add(MemoryListener *listener, > > > @@ -170,6 +189,10 @@ static void vhost_vdpa_listener_region_add(Memor= yListener *listener, > > > > > > llsize =3D int128_sub(llend, int128_make64(iova)); > > > > > > + if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH= )) { > > > > Let's move this in to vhost_vdpa_iotlb_batch_begin_once()? > > > > Sure > > > > + vhost_vdpa_iotlb_batch_begin_once(v); > > > + } > > > + > > > ret =3D vhost_vdpa_dma_map(v, iova, int128_get64(llsize), > > > vaddr, section->readonly); > > > if (ret) { > > > @@ -221,6 +244,10 @@ static void vhost_vdpa_listener_region_del(Memor= yListener *listener, > > > > > > llsize =3D int128_sub(llend, int128_make64(iova)); > > > > > > + if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH= )) { > > > + vhost_vdpa_iotlb_batch_begin_once(v); > > > + } > > > + > > > > Do we need to check vhost_vdpa_iotlb_batch_is_started() in the .commit? > > > > I don't follow you here. It's that comment in this position of the > patch for a reason? > > That checking is the one that allows qemu to skip the IOTLB_END write. So it looks to me the BATCH_END will be sent unconditionally in this patch? If yes, will this become a problem? Thanks > > > Others look good. > > > > Thanks > > > > > ret =3D vhost_vdpa_dma_unmap(v, iova, int128_get64(llsize)); > > > if (ret) { > > > error_report("vhost_vdpa dma unmap error!"); > > > @@ -234,7 +261,6 @@ static void vhost_vdpa_listener_region_del(Memory= Listener *listener, > > > * depends on the addnop(). > > > */ > > > static const MemoryListener vhost_vdpa_memory_listener =3D { > > > - .begin =3D vhost_vdpa_listener_begin, > > > .commit =3D vhost_vdpa_listener_commit, > > > .region_add =3D vhost_vdpa_listener_region_add, > > > .region_del =3D vhost_vdpa_listener_region_del, > > > -- > > > 2.27.0 > > > > > >