Hi, Thanks for the patch, comments below:
On Mon, Apr 01, 2019 at 02:18:43PM +0300, Yoni Bettan wrote: > The main goal is to add an example device to Qemu to be used as template or > guideline for contributors when they wish to create a new virtio device. > > Another reason for this device is to document "the right way" to write > a new virtio device in Qemu. > > This device is a simple device and its functionality is to increase its input > by 1. I believe we need a clearer description of what the device does, especially considering that you are using base 10 strings as input and output. (See additional comments about the string conversion below) > > The device driver is located at: > https://github.com/ybettan/QemuDeviceDrivers.git > > In addition I am writing a blog to give a logical overview of the virtio > protocol and a step-by-step guide to write a new virtio device. > This blog can be found at https://howtovms.wordpress.com. > > scripts/checkpatch.pl have some errors do to "//" (old style one line > comment), > those lines contains FIXMEs for the next version and will be removed. > > Signed-off-by: Yoni Bettan <ybet...@redhat.com> > --- > hw/virtio/Makefile.objs | 1 + > hw/virtio/virtio-example.c | 121 ++++++++++++++++++ > hw/virtio/virtio-pci.c | 49 +++++++ > hw/virtio/virtio-pci.h | 14 ++ > include/hw/pci/pci.h | 1 + > include/hw/virtio/virtio-example.h | 31 +++++ > .../standard-headers/linux/virtio_example.h | 8 ++ > include/standard-headers/linux/virtio_ids.h | 1 + > 8 files changed, 226 insertions(+) > create mode 100644 hw/virtio/virtio-example.c > create mode 100644 include/hw/virtio/virtio-example.h > create mode 100644 include/standard-headers/linux/virtio_example.h > > diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs > index 1b2799cfd8..7a6fb2505c 100644 > --- a/hw/virtio/Makefile.objs > +++ b/hw/virtio/Makefile.objs > @@ -7,6 +7,7 @@ common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o > common-obj-$(CONFIG_VIRTIO_MMIO) += virtio-mmio.o > obj-$(CONFIG_VIRTIO_BALLOON) += virtio-balloon.o > obj-$(CONFIG_VIRTIO_CRYPTO) += virtio-crypto.o > +obj-$(CONFIG_VIRTIO_CRYPTO) += virtio-example.o > obj-$(call land,$(CONFIG_VIRTIO_CRYPTO),$(CONFIG_VIRTIO_PCI)) += > virtio-crypto-pci.o > > obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o > diff --git a/hw/virtio/virtio-example.c b/hw/virtio/virtio-example.c > new file mode 100644 > index 0000000000..3c170f8022 > --- /dev/null > +++ b/hw/virtio/virtio-example.c > @@ -0,0 +1,121 @@ > +/* > + * A virtio device example. > + * > + * Copyright 2019 Red Hat, Inc. > + * Copyright 2019 Yoni Bettan <ybet...@redhat.com> > + * > + * This work is licensed under the terms of the GNU GPL, version 2 or > + * (at your option) any later version. See the COPYING file in the > + * top-level directory. > + */ > + > +#include "qemu/osdep.h" > +#include "qemu/iov.h" > +#include "hw/virtio/virtio.h" > +#include "hw/virtio/virtio-example.h" > + > +#define MAX_DATA_SIZE 10 > + > + > +/* > + * this function is called when the driver 'kick' the virtqueue. > + * since we can have more than 1 virtqueue we need the vq argument in order > to > + * know which one was kicked by the driver. > + */ > +static void handle_input(VirtIODevice *vdev, VirtQueue *vq) > +{ > + VirtQueueElement *elem; > + int data, len; > + char buf[MAX_DATA_SIZE]; > + > + /* check that virtqueue have at least 2 elements, input and output */ > + //FIXME: implement > + > + /* get the virtqueue input element sent from the driver */ > + elem = virtqueue_pop(vq, sizeof(VirtQueueElement)); > + > + /* read the input element (sg) into a buffer */ > + len = iov_to_buf(elem->in_sg, elem->out_num, 0, buf, MAX_DATA_SIZE); I believe you mean elem->in_num above. > + //FIXME: should i check buffer overflow, or iov_to_buf() is safe ? If iov_to_buf() didn't check the buffer size, checking it after it returned would be too late. > + if (len > MAX_DATA_SIZE) { > + goto error; > + } > + > + /* process the data */ > + data = atoi(buf); What if there's no null terminator on the input buffer? > + sprintf(buf, "%d", ++data); MAX_DATA_SIZE is 10, so if input data is "999999999" you will write beyond the end of the buffer. I suggest not dealing with the complexity of string conversion, and just do something simpler (like increasing every byte by 1). > + > + /* get the virtqueue output element sent from the driver */ > + elem = virtqueue_pop(vq, sizeof(VirtQueueElement)); I don't understand why you are using two separate buffers here. A single request may contain both input and output buffers. Also, I believe there's a risk here that the device will see the input buffer before the output buffer is added to the queue by the guest. > + > + /* write the result to the output element (sg) */ > + len = iov_from_buf(elem->in_sg, elem->in_num, 0, buf, MAX_DATA_SIZE); Why are you writing to in_sg instead of out_sg? > + //FIXME: should i check buffer overflow, or iov_from_buf() is safe ? > + > + /* push back the result into the virtqueue */ > + virtqueue_push(vq, elem, /*len=*/1); I suggest removing the "len=" comment in the next version. > + > + /* interrupt the driver */ > + virtio_notify(vdev, vq); These last two lines look right, but I would like somebody who works on virtio drivers to confirm. > + > + return; > + > +error: > + printf("ERROR: buffer overflow\n"); > + //FIXME: can we make the request fail ?, if iov_*_buf is safe we don't > need it I suggest simply dropping the data if there's no room on the output buffer. This way there's no need for any error handling. > +} > + > +/* > + * There is no currently defined feature bits, we still need this function > + * because the backend driver checks that VirtioDeviceClass.get_features is > + * initialized > + */ Maybe we should explain what get_features() does and why, as this is an example device implementation. > +static uint64_t get_features(VirtIODevice *vdev, uint64_t features, Error > **errp) > +{ > + return features; > +} > + > +static void virtio_example_device_realize(DeviceState *dev, Error **errp) > +{ > + VirtIODevice *vdev = VIRTIO_DEVICE(dev); > + VirtIOEXAMPLE *vexmp = VIRTIO_EXAMPLE(dev); > + > + /* base class initialization */ I'm not sure "base class initialization" is an accurate description of virtio_init(). Maybe the comment makes it more confusing. > + virtio_init(vdev, "virtio-example", VIRTIO_ID_EXAMPLE, > /*config_size=*/0); I suggest removing the "config_size=" comment in the next version. > + > + /* this device suppot 1 virtqueue */ > + vexmp->vq = virtio_add_queue(vdev, 8, handle_input); > +} > + > +static void virtio_example_device_unrealize(DeviceState *dev, Error **errp) > +{ > + VirtIODevice *vdev = VIRTIO_DEVICE(dev); > + > + /* base class cleanup */ > + virtio_cleanup(vdev); > +} > + > +static void virtio_example_class_init(ObjectClass *klass, void *data) > +{ > + DeviceClass *dc = DEVICE_CLASS(klass); > + VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass); > + > + set_bit(DEVICE_CATEGORY_MISC, dc->categories); > + vdc->realize = virtio_example_device_realize; > + vdc->unrealize = virtio_example_device_unrealize; > + vdc->get_features = get_features; > +} > + > +static const TypeInfo virtio_example_info = { > + .name = TYPE_VIRTIO_EXAMPLE, > + .parent = TYPE_VIRTIO_DEVICE, > + .instance_size = sizeof(VirtIOEXAMPLE), > + .class_init = virtio_example_class_init, > +}; > + > +static void virtio_register_types(void) > +{ > + type_register_static(&virtio_example_info); > +} > + > +type_init(virtio_register_types) > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > index 3a01fe90f0..99fc6ce79b 100644 > --- a/hw/virtio/virtio-pci.c > +++ b/hw/virtio/virtio-pci.c > @@ -2521,6 +2521,54 @@ static const TypeInfo virtio_rng_pci_info = { > .class_init = virtio_rng_pci_class_init, > }; > > +/* virtio-example-pci */ > + > +static void virtio_example_pci_realize(VirtIOPCIProxy *vpci_dev, Error > **errp) > +{ > + VirtIOExamplePCI *vexmp = VIRTIO_EXAMPLE_PCI(vpci_dev); > + DeviceState *vdev = DEVICE(&vexmp->vdev); > + Error *err = NULL; > + > + qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus)); > + object_property_set_bool(OBJECT(vdev), true, "realized", &err); > + if (err) { > + error_propagate(errp, err); > + return; > + } The 5 lines above can be replaced by: object_property_set_bool(OBJECT(vdev), true, "realized", errp); > + > +} > + > +static void virtio_example_pci_class_init(ObjectClass *klass, void *data) > +{ > + DeviceClass *dc = DEVICE_CLASS(klass); > + VirtioPCIClass *k = VIRTIO_PCI_CLASS(klass); > + PCIDeviceClass *pcidev_k = PCI_DEVICE_CLASS(klass); > + > + k->realize = virtio_example_pci_realize; > + set_bit(DEVICE_CATEGORY_MISC, dc->categories); > + > + pcidev_k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET; > + pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_EXAMPLE; > + pcidev_k->revision = VIRTIO_PCI_ABI_VERSION; > + pcidev_k->class_id = PCI_CLASS_OTHERS; > +} > + > +static void virtio_example_initfn(Object *obj) > +{ > + VirtIOExamplePCI *dev = VIRTIO_EXAMPLE_PCI(obj); > + > + virtio_instance_init_common(obj, &dev->vdev, sizeof(dev->vdev), > + TYPE_VIRTIO_EXAMPLE); > +} > + > +static const TypeInfo virtio_example_pci_info = { > + .name = TYPE_VIRTIO_EXAMPLE_PCI, > + .parent = TYPE_VIRTIO_PCI, > + .instance_size = sizeof(VirtIOExamplePCI), > + .instance_init = virtio_example_initfn, > + .class_init = virtio_example_pci_class_init, > +}; > + > /* virtio-input-pci */ > > static Property virtio_input_pci_properties[] = { > @@ -2693,6 +2741,7 @@ static const TypeInfo virtio_pci_bus_info = { > static void virtio_pci_register_types(void) > { > type_register_static(&virtio_rng_pci_info); > + type_register_static(&virtio_example_pci_info); > type_register_static(&virtio_input_pci_info); > type_register_static(&virtio_input_hid_pci_info); > type_register_static(&virtio_keyboard_pci_info); > diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h > index 813082b0d7..db3f5ec17d 100644 > --- a/hw/virtio/virtio-pci.h > +++ b/hw/virtio/virtio-pci.h > @@ -19,6 +19,7 @@ > #include "hw/virtio/virtio-blk.h" > #include "hw/virtio/virtio-net.h" > #include "hw/virtio/virtio-rng.h" > +#include "hw/virtio/virtio-example.h" > #include "hw/virtio/virtio-serial.h" > #include "hw/virtio/virtio-scsi.h" > #include "hw/virtio/virtio-balloon.h" > @@ -51,6 +52,7 @@ typedef struct VHostSCSIPCI VHostSCSIPCI; > typedef struct VHostUserSCSIPCI VHostUserSCSIPCI; > typedef struct VHostUserBlkPCI VHostUserBlkPCI; > typedef struct VirtIORngPCI VirtIORngPCI; > +typedef struct VirtIOExamplePCI VirtIOExamplePCI; > typedef struct VirtIOInputPCI VirtIOInputPCI; > typedef struct VirtIOInputHIDPCI VirtIOInputHIDPCI; > typedef struct VirtIOInputHostPCI VirtIOInputHostPCI; > @@ -339,6 +341,18 @@ struct VirtIORngPCI { > VirtIORNG vdev; > }; > > +/* > + * virtio-example-pci: This extends VirtioPCIProxy. > + */ > +#define TYPE_VIRTIO_EXAMPLE_PCI "virtio-example-pci" > +#define VIRTIO_EXAMPLE_PCI(obj) \ > + OBJECT_CHECK(VirtIOExamplePCI, (obj), TYPE_VIRTIO_EXAMPLE_PCI) > + > +struct VirtIOExamplePCI { > + VirtIOPCIProxy parent_obj; > + VirtIOEXAMPLE vdev; > +}; > + > /* > * virtio-input-pci: This extends VirtioPCIProxy. > */ > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h > index 990d6fcbde..c69d5997b7 100644 > --- a/include/hw/pci/pci.h > +++ b/include/hw/pci/pci.h > @@ -83,6 +83,7 @@ extern bool pci_available; > #define PCI_DEVICE_ID_VIRTIO_CONSOLE 0x1003 > #define PCI_DEVICE_ID_VIRTIO_SCSI 0x1004 > #define PCI_DEVICE_ID_VIRTIO_RNG 0x1005 > +#define PCI_DEVICE_ID_VIRTIO_EXAMPLE 0x1006 //FIXME: update to valid ID I'm not sure what to do about the device ID here. Should we really allocate a device ID for this example device? > #define PCI_DEVICE_ID_VIRTIO_9P 0x1009 > #define PCI_DEVICE_ID_VIRTIO_VSOCK 0x1012 > > diff --git a/include/hw/virtio/virtio-example.h > b/include/hw/virtio/virtio-example.h > new file mode 100644 > index 0000000000..c08db28e8f > --- /dev/null > +++ b/include/hw/virtio/virtio-example.h > @@ -0,0 +1,31 @@ > +/* > + * Virtio EXAMPLE Support > + * > + * Copyright Red Hat, Inc. 2019 > + * Copyright Yoni Bettan <ybet...@redhat.com> > + * > + * This work is licensed under the terms of the GNU GPL, version 2 or > + * (at your option) any later version. See the COPYING file in the > + * top-level directory. > + */ > + > +#ifndef QEMU_VIRTIO_EXAMPLE_H > +#define QEMU_VIRTIO_EXAMPLE_H > + > +#include "standard-headers/linux/virtio_example.h" > + > +#define TYPE_VIRTIO_EXAMPLE "virtio-example-device" > +#define VIRTIO_EXAMPLE(obj) \ > + OBJECT_CHECK(VirtIOEXAMPLE, (obj), TYPE_VIRTIO_EXAMPLE) > +#define VIRTIO_EXAMPLE_GET_PARENT_CLASS(obj) \ > + OBJECT_GET_PARENT_CLASS(obj, TYPE_VIRTIO_EXAMPLE) > + > +typedef struct VirtIOEXAMPLE { > + VirtIODevice parent_obj; > + > + /* Only one vq - guest puts buffer(s) on it when it needs computation */ > + VirtQueue *vq; > + > +} VirtIOEXAMPLE; > + > +#endif > diff --git a/include/standard-headers/linux/virtio_example.h > b/include/standard-headers/linux/virtio_example.h > new file mode 100644 > index 0000000000..6321c60c5c > --- /dev/null > +++ b/include/standard-headers/linux/virtio_example.h > @@ -0,0 +1,8 @@ > +#ifndef _LINUX_VIRTIO_EXAMPLE_H > +#define _LINUX_VIRTIO_EXAMPLE_H > +/* This header is BSD licensed so anyone can use the definitions to implement > + * compatible drivers/servers. */ > +#include "standard-headers/linux/virtio_ids.h" > +#include "standard-headers/linux/virtio_config.h" > + > +#endif /* _LINUX_VIRTIO_EXAMPLE_H */ > diff --git a/include/standard-headers/linux/virtio_ids.h > b/include/standard-headers/linux/virtio_ids.h > index 6d5c3b2d4f..30c189303b 100644 > --- a/include/standard-headers/linux/virtio_ids.h > +++ b/include/standard-headers/linux/virtio_ids.h > @@ -43,5 +43,6 @@ > #define VIRTIO_ID_INPUT 18 /* virtio input */ > #define VIRTIO_ID_VSOCK 19 /* virtio vsock transport */ > #define VIRTIO_ID_CRYPTO 20 /* virtio crypto */ > +#define VIRTIO_ID_EXAMPLE 21 /* virtio example */ > Same question about device ID here. Should we really allocate a device ID for this example device? Also, standard-headers is supposed to be copied from the Linux source tree, and not touched by any patch except when running update-linux-headers.sh. -- Eduardo