Re: [PATCH] [PATCH 1/3] virtio infrastructure

[Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

Hi Dor,

I can't tell if you made any changes to this series.  I have to look 
back to my notes, but I believe it would be okay to pull this series 
into KVM.  I still need to spend some time updating the patchset to be 
more friendly for QEMU though before resubmitting to qemu-devel.  Any 
help on making it more cross-architecture friendly would be appreciated!

Regards,

Anthony Liguori

Dor.Laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org wrote:
> From: Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
>
> This patch implements the basic infrastructure for virtio devices.  These
> devices are exposed to the guest as real PCI devices.  The PCI vendor/device
> IDs have been donated by Qumranet and the subsystem IDs are used to distinguish
> the virtio device itself.
>
> Virtio provides an abstraction for performing guest=>host and host=>guest
> communications.  It also provides a standard ring queue interface and discovery
> mechanism.  Finally, virtio provides a simple mechanism for passing
> configuration between host and guest.
>
> In this virtio implementation, we provide these things via normal PCI
> operations.  The Linux kernel support for this virtio device is pending in
> Rusty's virtio patch queue[1].  They should be submitted once the merge window
> opens again.
>
> Some future TODOs are to use endian/alignment safe routines when accessing the
> virtqueue so that mixed mode host/guests are supported.
>
> [1] http://ozlabs.org/~rusty/kernel/hg
>
> Signed-off-by: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> Cc: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
> Cc: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
> Cc: Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
> ---
>  qemu/Makefile.target |    3 +
>  qemu/hw/virtio.c     |  422 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  qemu/hw/virtio.h     |  143 +++++++++++++++++
>  3 files changed, 568 insertions(+), 0 deletions(-)
>  create mode 100644 qemu/hw/virtio.c
>  create mode 100644 qemu/hw/virtio.h
>
> diff --git a/qemu/Makefile.target b/qemu/Makefile.target
> index 12fb043..8b5853b 100644
> --- a/qemu/Makefile.target
> +++ b/qemu/Makefile.target
> @@ -463,6 +463,9 @@ VL_OBJS += rtl8139.o
>  # PCI Hypercall
>  VL_OBJS+= hypercall.o
>
> +# virtio devices
> +VL_OBJS += virtio.o
> +
>  ifeq ($(TARGET_BASE_ARCH), i386)
>  # Hardware support
>  VL_OBJS+= ide.o pckbd.o ps2.o vga.o $(SOUND_HW) dma.o
> diff --git a/qemu/hw/virtio.c b/qemu/hw/virtio.c
> new file mode 100644
> index 0000000..6a1d380
> --- /dev/null
> +++ b/qemu/hw/virtio.c
> @@ -0,0 +1,422 @@
> +/*
> + * Virtio Support
> + *
> + * Copyright IBM, Corp. 2007
> + *
> + * Authors:
> + *  Anthony Liguori   <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include <inttypes.h>
> +#include <err.h>
> +
> +#include "virtio.h"
> +#include "sysemu.h"
> +
> +/* from Linux's linux/virtio_pci.h */
> +
> +/* A 32-bit r/o bitmask of the features supported by the host */
> +#define VIRTIO_PCI_HOST_FEATURES	0
> +
> +/* A 32-bit r/w bitmask of features activated by the guest */
> +#define VIRTIO_PCI_GUEST_FEATURES	4
> +
> +/* A 32-bit r/w PFN for the currently selected queue */
> +#define VIRTIO_PCI_QUEUE_PFN		8
> +
> +/* A 16-bit r/o queue size for the currently selected queue */
> +#define VIRTIO_PCI_QUEUE_NUM		12
> +
> +/* A 16-bit r/w queue selector */
> +#define VIRTIO_PCI_QUEUE_SEL		14
> +
> +/* A 16-bit r/w queue notifier */
> +#define VIRTIO_PCI_QUEUE_NOTIFY		16
> +
> +/* An 8-bit device status register.  */
> +#define VIRTIO_PCI_STATUS		18
> +
> +/* An 8-bit r/o interrupt status register.  Reading the value will return the
> + * current contents of the ISR and will also clear it.  This is effectively
> + * a read-and-acknowledge. */
> +#define VIRTIO_PCI_ISR			19
> +
> +#define VIRTIO_PCI_CONFIG		20
> +
> +/* QEMU doesn't strictly need write barriers since everything runs in
> + * lock-step.  We'll leave the calls to wmb() in though to make it obvious for
> + * KVM or if kqemu gets SMP support.
> + */
> +#define wmb() do { } while (0)
> +
> +/* virt queue functions */
> +
> +static void virtqueue_init(VirtQueue *vq, void *p)
> +{
> +    vq->vring.desc = p;
> +    vq->vring.avail = p + vq->vring.num * sizeof(VRingDesc);
> +    vq->vring.used = (void *)TARGET_PAGE_ALIGN((unsigned long)&vq->vring.avail->ring[vq->vring.num]);
> +}
> +
> +static unsigned virtqueue_next_desc(VirtQueue *vq, unsigned int i)
> +{
> +    unsigned int next;
> +
> +    /* If this descriptor says it doesn't chain, we're done. */
> +    if (!(vq->vring.desc[i].flags & VRING_DESC_F_NEXT))
> +	return vq->vring.num;
> +
> +    /* Check they're not leading us off end of descriptors. */
> +    next = vq->vring.desc[i].next;
> +    /* Make sure compiler knows to grab that: we don't want it changing! */
> +    wmb();
> +
> +    if (next >= vq->vring.num)
> +	errx(1, "Desc next is %u", next);
> +
> +    return next;
> +}
> +
> +void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
> +		    unsigned int len)
> +{
> +    VRingUsedElem *used;
> +
> +    /* Get a pointer to the next entry in the used ring. */
> +    used = &vq->vring.used->ring[vq->vring.used->idx % vq->vring.num];
> +    used->id = elem->index;
> +    used->len = len;
> +    /* Make sure buffer is written before we update index. */
> +    wmb();
> +    vq->vring.used->idx++;
> +}
> +
> +int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem)
> +{
> +    unsigned int i, head;
> +    unsigned int position;
> +
> +    /* Check it isn't doing very strange things with descriptor numbers. */
> +    if ((uint16_t)(vq->vring.avail->idx - vq->last_avail_idx) > vq->vring.num)
> +	errx(1, "Guest moved used index from %u to %u",
> +	     vq->last_avail_idx, vq->vring.avail->idx);
> +
> +    /* If there's nothing new since last we looked, return invalid. */
> +    if (vq->vring.avail->idx == vq->last_avail_idx)
> +	return 0;
> +
> +    /* Grab the next descriptor number they're advertising, and increment
> +     * the index we've seen. */
> +    head = vq->vring.avail->ring[vq->last_avail_idx++ % vq->vring.num];
> +
> +    /* If their number is silly, that's a fatal mistake. */
> +    if (head >= vq->vring.num)
> +	errx(1, "Guest says index %u is available", head);
> +
> +    /* When we start there are none of either input nor output. */
> +    position = elem->out_num = elem->in_num = 0;
> +
> +    i = head;
> +    do {
> +	struct iovec *sg;
> +
> +	if ((vq->vring.desc[i].addr + vq->vring.desc[i].len) > ram_size)
> +	    errx(1, "Guest sent invalid pointer");
> +
> +	if (vq->vring.desc[i].flags & VRING_DESC_F_WRITE)
> +	    sg = &elem->in_sg[elem->in_num++];
> +	else
> +	    sg = &elem->out_sg[elem->out_num++];
> +
> +	/* Grab the first descriptor, and check it's OK. */
> +	sg->iov_len = vq->vring.desc[i].len;
> +	sg->iov_base = phys_ram_base + vq->vring.desc[i].addr;
> +
> +	/* If we've got too many, that implies a descriptor loop. */
> +	if ((elem->in_num + elem->out_num) > vq->vring.num)
> +	    errx(1, "Looped descriptor");
> +    } while ((i = virtqueue_next_desc(vq, i)) != vq->vring.num);
> +
> +    elem->index = head;
> +
> +    return elem->in_num + elem->out_num;
> +}
> +
> +/* virtio device */
> +
> +static VirtIODevice *to_virtio_device(PCIDevice *pci_dev)
> +{
> +    return (VirtIODevice *)pci_dev;
> +}
> +
> +static void virtio_update_irq(VirtIODevice *vdev)
> +{
> +    qemu_set_irq(vdev->pci_dev.irq[0], vdev->isr & 1);
> +}
> +
> +static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
> +{
> +    VirtIODevice *vdev = to_virtio_device(opaque);
> +    ram_addr_t pa;
> +
> +    addr -= vdev->addr;
> +
> +    switch (addr) {
> +    case VIRTIO_PCI_GUEST_FEATURES:
> +	if (vdev->set_features)
> +	    vdev->set_features(vdev, val);
> +	vdev->features = val;
> +	break;
> +    case VIRTIO_PCI_QUEUE_PFN:
> +	pa = (ram_addr_t)val << TARGET_PAGE_BITS;
> +	vdev->vq[vdev->queue_sel].pfn = val;
> +	if (pa == 0) {
> +	    vdev->vq[vdev->queue_sel].vring.desc = NULL;
> +	    vdev->vq[vdev->queue_sel].vring.avail = NULL;
> +	    vdev->vq[vdev->queue_sel].vring.used = NULL;
> +	} else if (pa < (ram_size - TARGET_PAGE_SIZE)) {
> +	    virtqueue_init(&vdev->vq[vdev->queue_sel], phys_ram_base + pa);
> +	    /* FIXME if pa == 0, deal with device tear down */
> +	}
> +	break;
> +    case VIRTIO_PCI_QUEUE_SEL:
> +	if (val < VIRTIO_PCI_QUEUE_MAX)
> +	    vdev->queue_sel = val;
> +	break;
> +    case VIRTIO_PCI_QUEUE_NOTIFY:
> +	if (val < VIRTIO_PCI_QUEUE_MAX && vdev->vq[val].vring.desc)
> +	    vdev->vq[val].handle_output(vdev, &vdev->vq[val]);
> +	break;
> +    case VIRTIO_PCI_STATUS:
> +	vdev->status = val & 0xFF;
> +	break;
> +    }
> +}
> +
> +static uint32_t virtio_ioport_read(void *opaque, uint32_t addr)
> +{
> +    VirtIODevice *vdev = to_virtio_device(opaque);
> +    uint32_t ret = 0xFFFFFFFF;
> +
> +    addr -= vdev->addr;
> +
> +    switch (addr) {
> +    case VIRTIO_PCI_HOST_FEATURES:
> +	ret = vdev->get_features(vdev);
> +	break;
> +    case VIRTIO_PCI_GUEST_FEATURES:
> +	ret = vdev->features;
> +	break;
> +    case VIRTIO_PCI_QUEUE_PFN:
> +	ret = vdev->vq[vdev->queue_sel].pfn;
> +	break;
> +    case VIRTIO_PCI_QUEUE_NUM:
> +	ret = vdev->vq[vdev->queue_sel].vring.num;
> +	break;
> +    case VIRTIO_PCI_QUEUE_SEL:
> +	ret = vdev->queue_sel;
> +	break;
> +    case VIRTIO_PCI_STATUS:
> +	ret = vdev->status;
> +	break;
> +    case VIRTIO_PCI_ISR:
> +	/* reading from the ISR also clears it. */
> +	ret = vdev->isr;
> +	vdev->isr = 0;
> +	virtio_update_irq(vdev);
> +	break;
> +    default:
> +	break;
> +    }
> +
> +    return ret;
> +}
> +
> +static uint32_t virtio_config_readb(void *opaque, uint32_t addr)
> +{
> +    VirtIODevice *vdev = opaque;
> +    uint8_t val;
> +
> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
> +    if (addr > (vdev->config_len - sizeof(val)))
> +	return (uint32_t)-1;
> +
> +    memcpy(&val, vdev->config + addr, sizeof(val));
> +    return val;
> +}
> +
> +static uint32_t virtio_config_readw(void *opaque, uint32_t addr)
> +{
> +    VirtIODevice *vdev = opaque;
> +    uint16_t val;
> +
> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
> +    if (addr > (vdev->config_len - sizeof(val)))
> +	return (uint32_t)-1;
> +
> +    memcpy(&val, vdev->config + addr, sizeof(val));
> +    return val;
> +}
> +
> +static uint32_t virtio_config_readl(void *opaque, uint32_t addr)
> +{
> +    VirtIODevice *vdev = opaque;
> +    uint32_t val;
> +
> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
> +    if (addr > (vdev->config_len - sizeof(val)))
> +	return (uint32_t)-1;
> +
> +    memcpy(&val, vdev->config + addr, sizeof(val));
> +    return val;
> +}
> +
> +static void virtio_config_writeb(void *opaque, uint32_t addr, uint32_t data)
> +{
> +    VirtIODevice *vdev = opaque;
> +    uint8_t val = data;
> +
> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
> +    if (addr > (vdev->config_len - sizeof(val)))
> +	return;
> +
> +    memcpy(vdev->config + addr, &val, sizeof(val));
> +}
> +
> +static void virtio_config_writew(void *opaque, uint32_t addr, uint32_t data)
> +{
> +    VirtIODevice *vdev = opaque;
> +    uint16_t val = data;
> +
> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
> +    if (addr > (vdev->config_len - sizeof(val)))
> +	return;
> +
> +    memcpy(vdev->config + addr, &val, sizeof(val));
> +}
> +
> +static void virtio_config_writel(void *opaque, uint32_t addr, uint32_t data)
> +{
> +    VirtIODevice *vdev = opaque;
> +    uint32_t val = data;
> +
> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
> +    if (addr > (vdev->config_len - sizeof(val)))
> +	return;
> +
> +    memcpy(vdev->config + addr, &val, sizeof(val));
> +}
> +
> +static void virtio_map(PCIDevice *pci_dev, int region_num,
> +		       uint32_t addr, uint32_t size, int type)
> +{
> +    VirtIODevice *vdev = to_virtio_device(pci_dev);
> +    int i;
> +
> +    vdev->addr = addr;
> +    for (i = 0; i < 3; i++) {
> +	register_ioport_write(addr, 20, 1 << i, virtio_ioport_write, vdev);
> +	register_ioport_read(addr, 20, 1 << i, virtio_ioport_read, vdev);
> +    }
> +
> +    if (vdev->config_len) {
> +	register_ioport_write(addr + 20, vdev->config_len, 1,
> +			      virtio_config_writeb, vdev);
> +	register_ioport_write(addr + 20, vdev->config_len, 2,
> +			      virtio_config_writew, vdev);
> +	register_ioport_write(addr + 20, vdev->config_len, 4,
> +			      virtio_config_writel, vdev);
> +	register_ioport_read(addr + 20, vdev->config_len, 1,
> +			     virtio_config_readb, vdev);
> +	register_ioport_read(addr + 20, vdev->config_len, 2,
> +			     virtio_config_readw, vdev);
> +	register_ioport_read(addr + 20, vdev->config_len, 4,
> +			     virtio_config_readl, vdev);
> +
> +	vdev->update_config(vdev, vdev->config);
> +    }
> +}
> +
> +VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
> +			    void (*handle_output)(VirtIODevice *, VirtQueue *))
> +{
> +    int i;
> +
> +    for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {
> +	if (vdev->vq[i].vring.num == 0)
> +	    break;
> +    }
> +
> +    if (i == VIRTIO_PCI_QUEUE_MAX || queue_size > VIRTQUEUE_MAX_SIZE)
> +	abort();
> +
> +    vdev->vq[i].vring.num = queue_size;
> +    vdev->vq[i].handle_output = handle_output;
> +    vdev->vq[i].index = i;
> +
> +    return &vdev->vq[i];
> +}
> +
> +void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)
> +{
> +    if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> +	return;
> +
> +    vdev->isr = 1;
> +    virtio_update_irq(vdev);
> +}
> +
> +VirtIODevice *virtio_init_pci(PCIBus *bus, const char *name,
> +			      uint16_t vendor, uint16_t device,
> +			      uint16_t subvendor, uint16_t subdevice,
> +			      uint8_t class_code, uint8_t subclass_code,
> +			      uint8_t pif, size_t config_size,
> +			      size_t struct_size)
> +{
> +    VirtIODevice *vdev;
> +    PCIDevice *pci_dev;
> +    uint8_t *config;
> +
> +    pci_dev = pci_register_device(bus, name, struct_size,
> +				  -1, NULL, NULL);
> +    vdev = to_virtio_device(pci_dev);
> +
> +    vdev->status = 0;
> +    vdev->isr = 0;
> +    vdev->queue_sel = 0;
> +    memset(vdev->vq, 0, sizeof(vdev->vq));
> +
> +    config = pci_dev->config;
> +    config[0x00] = vendor & 0xFF;
> +    config[0x01] = (vendor >> 8) & 0xFF;
> +    config[0x02] = device & 0xFF;
> +    config[0x03] = (device >> 8) & 0xFF;
> +
> +    config[0x09] = pif;
> +    config[0x0a] = subclass_code;
> +    config[0x0b] = class_code;
> +    config[0x0e] = 0x00;
> +
> +    config[0x2c] = subvendor & 0xFF;
> +    config[0x2d] = (subvendor >> 8) & 0xFF;
> +    config[0x2e] = subdevice & 0xFF;
> +    config[0x2f] = (subdevice >> 8) & 0xFF;
> +
> +    config[0x3d] = 1;
> +
> +    vdev->name = name;
> +    vdev->config_len = config_size;
> +    if (vdev->config_len)
> +	vdev->config = qemu_mallocz(config_size);
> +    else
> +	vdev->config = NULL;
> +
> +    pci_register_io_region(pci_dev, 0, 20 + config_size, PCI_ADDRESS_SPACE_IO,
> +			   virtio_map);
> +
> +    return vdev;
> +}
> diff --git a/qemu/hw/virtio.h b/qemu/hw/virtio.h
> new file mode 100644
> index 0000000..dee97ba
> --- /dev/null
> +++ b/qemu/hw/virtio.h
> @@ -0,0 +1,143 @@
> +/*
> + * Virtio Support
> + *
> + * Copyright IBM, Corp. 2007
> + *
> + * Authors:
> + *  Anthony Liguori   <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef _QEMU_VIRTIO_H
> +#define _QEMU_VIRTIO_H
> +
> +#include <sys/uio.h>
> +#include "hw.h"
> +#include "pci.h"
> +
> +/* from Linux's linux/virtio_config.h */
> +
> +/* Status byte for guest to report progress, and synchronize features. */
> +/* We have seen device and processed generic fields (VIRTIO_CONFIG_F_VIRTIO) */
> +#define VIRTIO_CONFIG_S_ACKNOWLEDGE	1
> +/* We have found a driver for the device. */
> +#define VIRTIO_CONFIG_S_DRIVER		2
> +/* Driver has used its parts of the config, and is happy */
> +#define VIRTIO_CONFIG_S_DRIVER_OK	4
> +/* We've given up on this device. */
> +#define VIRTIO_CONFIG_S_FAILED		0x80
> +
> +/* from Linux's linux/virtio_ring.h */
> +
> +/* This marks a buffer as continuing via the next field. */
> +#define VRING_DESC_F_NEXT	1
> +/* This marks a buffer as write-only (otherwise read-only). */
> +#define VRING_DESC_F_WRITE	2
> +
> +/* This means don't notify other side when buffer added. */
> +#define VRING_USED_F_NO_NOTIFY	1
> +/* This means don't interrupt guest when buffer consumed. */
> +#define VRING_AVAIL_F_NO_INTERRUPT	1
> +
> +typedef struct VirtQueue VirtQueue;
> +typedef struct VirtIODevice VirtIODevice;
> +
> +typedef struct VRingDesc
> +{
> +    uint64_t addr;
> +    uint32_t len;
> +    uint16_t flags;
> +    uint16_t next;
> +} VRingDesc;
> +
> +typedef struct VRingAvail
> +{
> +    uint16_t flags;
> +    uint16_t idx;
> +    uint16_t ring[0];
> +} VRingAvail;
> +
> +typedef struct VRingUsedElem
> +{
> +    uint32_t id;
> +    uint32_t len;
> +} VRingUsedElem;
> +
> +typedef struct VRingUsed
> +{
> +    uint16_t flags;
> +    uint16_t idx;
> +    VRingUsedElem ring[0];
> +} VRingUsed;
> +
> +typedef struct VRing
> +{
> +    unsigned int num;
> +    VRingDesc *desc;
> +    VRingAvail *avail;
> +    VRingUsed *used;
> +} VRing;
> +
> +struct VirtQueue
> +{
> +    VRing vring;
> +    uint32_t pfn;
> +    uint16_t last_avail_idx;
> +    void (*handle_output)(VirtIODevice *vdev, VirtQueue *vq);
> +    int index;
> +};
> +
> +#define VIRTQUEUE_MAX_SIZE 1024
> +
> +typedef struct VirtQueueElement
> +{
> +    unsigned int index;
> +    unsigned int out_num;
> +    unsigned int in_num;
> +    struct iovec in_sg[VIRTQUEUE_MAX_SIZE];
> +    struct iovec out_sg[VIRTQUEUE_MAX_SIZE];
> +} VirtQueueElement;
> +
> +#define VIRTIO_PCI_QUEUE_MAX	16
> +
> +struct VirtIODevice
> +{
> +    PCIDevice pci_dev;
> +    const char *name;
> +    uint32_t addr;
> +    uint16_t vendor;
> +    uint16_t device;
> +    uint8_t status;
> +    uint8_t isr;
> +    uint16_t queue_sel;
> +    uint32_t features;
> +    size_t config_len;
> +    void *config;
> +    uint32_t (*get_features)(VirtIODevice *vdev);
> +    void (*set_features)(VirtIODevice *vdev, uint32_t val);
> +    void (*update_config)(VirtIODevice *vdev, uint8_t *config);
> +    VirtQueue vq[VIRTIO_PCI_QUEUE_MAX];
> +};
> +
> +VirtIODevice *virtio_init_pci(PCIBus *bus, const char *name,
> +			      uint16_t vendor, uint16_t device,
> +			      uint16_t subvendor, uint16_t subdevice,
> +			      uint8_t class_code, uint8_t subclass_code,
> +			      uint8_t pif, size_t config_size,
> +			      size_t struct_size);
> +
> +VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
> +			    void (*handle_output)(VirtIODevice *,
> +						  VirtQueue *));
> +
> +void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
> +		    unsigned int len);
> +
> +int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem);
> +
> +void virtio_notify(VirtIODevice *vdev, VirtQueue *vq);
> +
> +#endif
>   


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