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Tsirkin" , Stefano Garzarella , Cornelia Huck , Luigi Rizzo , Giuseppe Lettieri , Vincenzo Maffione , Eric Blake , Markus Armbruster Subject: [RFC PATCH v4 07/14] virtio-pci: implement support for extended features Date: Wed, 23 Jul 2025 21:31:27 +0200 Message-ID: <8e8a91adcbf4e37c7a5e086780e1000d3b3298d3.1753297661.git.pabeni@redhat.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=pabeni@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.377, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1753299424762116600 Content-Type: text/plain; charset="utf-8" Extend the features configuration space to 128 bits. If the virtio device supports any extended features, allow the common read/write operation to access all of it, otherwise keep exposing only the lower 64 bits. On migration, save the 128 bit version of the features only if the upper bits are non zero. Relay on reset to clear all the feature space before load. Signed-off-by: Paolo Abeni --- v3 -> v4: - use new virtio_features macro names - move the build bug before vmstate_virtio_pci_modern_state_sub v2 -> v3: - drop the pre_load/post_load trickery and relay on reset zeroing the features instead. - avoid union usage, just increase guest_features size and use SUB_ARRAY. - drop unneeded '!!' - _array -> _ex v1 -> v2: - use separate VMStateDescription and pre/post load to avoid breaking migration - clear proxy features on device reset --- hw/virtio/virtio-pci.c | 69 +++++++++++++++++++++++++++++----- include/hw/virtio/virtio-pci.h | 2 +- 2 files changed, 61 insertions(+), 10 deletions(-) diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c index 767216d795..bcc4d48c2c 100644 --- a/hw/virtio/virtio-pci.c +++ b/hw/virtio/virtio-pci.c @@ -109,6 +109,29 @@ static const VMStateDescription vmstate_virtio_pci_mod= ern_queue_state =3D { } }; =20 +static bool virtio_pci_modern_state_features128_needed(void *opaque) +{ + VirtIOPCIProxy *proxy =3D opaque; + uint32_t features =3D 0; + int i; + + for (i =3D 2; i < ARRAY_SIZE(proxy->guest_features); ++i) { + features |=3D proxy->guest_features[i]; + } + return features; +} + +static const VMStateDescription vmstate_virtio_pci_modern_state_features12= 8 =3D { + .name =3D "virtio_pci/modern_state/features128", + .version_id =3D 1, + .minimum_version_id =3D 1, + .needed =3D &virtio_pci_modern_state_features128_needed, + .fields =3D (const VMStateField[]) { + VMSTATE_UINT32_SUB_ARRAY(guest_features, VirtIOPCIProxy, 2, 2), + VMSTATE_END_OF_LIST() + } +}; + static bool virtio_pci_modern_state_needed(void *opaque) { VirtIOPCIProxy *proxy =3D opaque; @@ -116,6 +139,11 @@ static bool virtio_pci_modern_state_needed(void *opaqu= e) return virtio_pci_modern(proxy); } =20 +/* + * Avoid silently breaking migration should the feature space increase + * even more in the (far away) future + */ +QEMU_BUILD_BUG_ON(VIRTIO_FEATURES_NU32S !=3D 4); static const VMStateDescription vmstate_virtio_pci_modern_state_sub =3D { .name =3D "virtio_pci/modern_state", .version_id =3D 1, @@ -124,11 +152,15 @@ static const VMStateDescription vmstate_virtio_pci_mo= dern_state_sub =3D { .fields =3D (const VMStateField[]) { VMSTATE_UINT32(dfselect, VirtIOPCIProxy), VMSTATE_UINT32(gfselect, VirtIOPCIProxy), - VMSTATE_UINT32_ARRAY(guest_features, VirtIOPCIProxy, 2), + VMSTATE_UINT32_SUB_ARRAY(guest_features, VirtIOPCIProxy, 0, 2), VMSTATE_STRUCT_ARRAY(vqs, VirtIOPCIProxy, VIRTIO_QUEUE_MAX, 0, vmstate_virtio_pci_modern_queue_state, VirtIOPCIQueue), VMSTATE_END_OF_LIST() + }, + .subsections =3D (const VMStateDescription * const []) { + &vmstate_virtio_pci_modern_state_features128, + NULL } }; =20 @@ -1477,6 +1509,13 @@ int virtio_pci_add_shm_cap(VirtIOPCIProxy *proxy, return virtio_pci_add_mem_cap(proxy, &cap.cap); } =20 +static int virtio_pci_select_max(const VirtIODevice *vdev) +{ + return virtio_features_use_ex(vdev->host_features_ex) ? + VIRTIO_FEATURES_NU32S : + 2; +} + static uint64_t virtio_pci_common_read(void *opaque, hwaddr addr, unsigned size) { @@ -1494,18 +1533,21 @@ static uint64_t virtio_pci_common_read(void *opaque= , hwaddr addr, val =3D proxy->dfselect; break; case VIRTIO_PCI_COMMON_DF: - if (proxy->dfselect <=3D 1) { + if (proxy->dfselect < virtio_pci_select_max(vdev)) { VirtioDeviceClass *vdc =3D VIRTIO_DEVICE_GET_CLASS(vdev); =20 - val =3D (vdev->host_features & ~vdc->legacy_features) >> - (32 * proxy->dfselect); + val =3D vdev->host_features_ex[proxy->dfselect >> 1] >> + (32 * (proxy->dfselect & 1)); + if (proxy->dfselect <=3D 1) { + val &=3D (~vdc->legacy_features) >> (32 * proxy->dfselect); + } } break; case VIRTIO_PCI_COMMON_GFSELECT: val =3D proxy->gfselect; break; case VIRTIO_PCI_COMMON_GF: - if (proxy->gfselect < ARRAY_SIZE(proxy->guest_features)) { + if (proxy->gfselect < virtio_pci_select_max(vdev)) { val =3D proxy->guest_features[proxy->gfselect]; } break; @@ -1588,11 +1630,18 @@ static void virtio_pci_common_write(void *opaque, h= waddr addr, proxy->gfselect =3D val; break; case VIRTIO_PCI_COMMON_GF: - if (proxy->gfselect < ARRAY_SIZE(proxy->guest_features)) { + if (proxy->gfselect < virtio_pci_select_max(vdev)) { + uint64_t features[VIRTIO_FEATURES_NU64S]; + int i; + proxy->guest_features[proxy->gfselect] =3D val; - virtio_set_features(vdev, - (((uint64_t)proxy->guest_features[1]) << 3= 2) | - proxy->guest_features[0]); + virtio_features_clear(features); + for (i =3D 0; i < ARRAY_SIZE(proxy->guest_features); ++i) { + uint64_t cur =3D proxy->guest_features[i]; + + features[i >> 1] |=3D cur << ((i & 1) * 32); + } + virtio_set_features_ex(vdev, features); } break; case VIRTIO_PCI_COMMON_MSIX: @@ -2311,6 +2360,8 @@ static void virtio_pci_reset(DeviceState *qdev) virtio_bus_reset(bus); msix_unuse_all_vectors(&proxy->pci_dev); =20 + memset(proxy->guest_features, 0, sizeof(proxy->guest_features)); + for (i =3D 0; i < VIRTIO_QUEUE_MAX; i++) { proxy->vqs[i].enabled =3D 0; proxy->vqs[i].reset =3D 0; diff --git a/include/hw/virtio/virtio-pci.h b/include/hw/virtio/virtio-pci.h index eab5394898..639752977e 100644 --- a/include/hw/virtio/virtio-pci.h +++ b/include/hw/virtio/virtio-pci.h @@ -158,7 +158,7 @@ struct VirtIOPCIProxy { uint32_t nvectors; uint32_t dfselect; uint32_t gfselect; - uint32_t guest_features[2]; + uint32_t guest_features[VIRTIO_FEATURES_NU32S]; VirtIOPCIQueue vqs[VIRTIO_QUEUE_MAX]; =20 VirtIOIRQFD *vector_irqfd; --=20 2.50.0