Re: [SeaBIOS] [PATCHv2] Support for booting from virtio disks

[Gleb Natapov]

On Mon, May 10, 2010 at 10:48:42AM -0500, Anthony Liguori wrote:
> On 05/10/2010 03:11 AM, Gleb Natapov wrote:
> > This patch adds native support for booting from virtio disks to Seabios.
> >
> > Signed-off-by: Gleb Natapov
>
> A related problem that I think we need to think about how we solve
> is indicating to Seabios which device we want to boot from
>
> With your patch, a user can select a virtio device explicitly or if
> they use only one virtio device, it will Just Work.
>
> However, if a user uses IDE and virtio, or a user has multiple
> disks, they cannot select a device via -boot.

Isn't this problem unrelated to this patch?  I mean if I start qemu with
two ide devices can I specify from qemu command line which one I want to
boot from?
> Is this something we need to address?  I don't think we'd break
> libvirt if we didn't.
>
> Regards,
>
> Anthony Liguori
> > Changelog:
> >  v1->v2:
> > free memory in case of vq initialization error.
> > change license of virtio ring/pci to LGPLv3 with permission
> > of Laurent Vivier (aka the author).
> >
> > diff --git a/Makefile b/Makefile
> > index 327a1bf..d0b8881 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -14,7 +14,8 @@ OUT=out/
> >  SRCBOTH=misc.c pmm.c stacks.c output.c util.c block.c floppy.c ata.c mouse.c \
> >          kbd.c pci.c serial.c clock.c pic.c cdrom.c ps2port.c smp.c resume.c \
> >          pnpbios.c pirtable.c vgahooks.c ramdisk.c pcibios.c blockcmd.c \
> >    usb.c usb-uhci.c usb-ohci.c usb-ehci.c usb-hid.c usb-msc.c
> >    usb.c usb-uhci.c usb-ohci.c usb-ehci.c usb-hid.c usb-msc.c \
> >    virtio-ring.c virtio-pci.c virtio-blk.c
> >
> > SRC16=$(SRCBOTH) system.c disk.c apm.c font.c
> >  SRC32FLAT=$(SRCBOTH) post.c shadow.c memmap.c coreboot.c boot.c \
> >        acpi.c smm.c mptable.c smbios.c pciinit.c optionroms.c mtrr.c \
> > diff --git a/src/block.c b/src/block.c
> > index ddf441f..b6b1902 100644
> > --- a/src/block.c
> > +++ b/src/block.c
> > @@ -11,6 +11,7 @@
> >  #include "util.h" // dprintf
> >  #include "ata.h" // process_ata_op
> >  #include "usb-msc.h" // process_usb_op
> > +#include "virtio-blk.h" // process_virtio_op
> >
> > struct drives_s Drives VAR16VISIBLE;
> >
> > @@ -289,6 +290,8 @@ process_op(struct disk_op_s *op)
> >          return process_cdemu_op(op);
> >      case DTYPE_USB:
> >          return process_usb_op(op);
> > case DTYPE_VIRTIO:
> > return process_virtio_op(op);
> > default:
> >     op->count = 0;
> >     return DISK_RET_EPARAM;
> >
> > diff --git a/src/config.h b/src/config.h
> > index b101174..ad569c6 100644
> > --- a/src/config.h
> > +++ b/src/config.h
> > @@ -136,6 +136,9 @@
> >  #define CONFIG_SUBMODEL_ID   0x00
> >  #define CONFIG_BIOS_REVISION 0x01
> >
> > +// Support boot from virtio storage
> > +#define CONFIG_VIRTIO_BLK 1
> >
> > // Various memory addresses used by the code.
> >  #define BUILD_STACK_ADDR          0x7000
> >  #define BUILD_S3RESUME_STACK_ADDR 0x1000
> > diff --git a/src/disk.h b/src/disk.h
> > index 0cd1b74..9e5b083 100644
> > --- a/src/disk.h
> > +++ b/src/disk.h
> > @@ -197,6 +197,7 @@ struct drive_s {
> >  #define DTYPE_RAMDISK  0x04
> >  #define DTYPE_CDEMU    0x05
> >  #define DTYPE_USB      0x06
> > +#define DTYPE_VIRTIO   0x07
> >
> > #define MAXDESCSIZE 80
> >
> > diff --git a/src/pci_ids.h b/src/pci_ids.h
> > index 1800f1d..e1cded2 100644
> > --- a/src/pci_ids.h
> > +++ b/src/pci_ids.h
> > @@ -2605,3 +2605,6 @@
> >  #define PCI_DEVICE_ID_RME_DIGI32	0x9896
> >  #define PCI_DEVICE_ID_RME_DIGI32_PRO	0x9897
> >  #define PCI_DEVICE_ID_RME_DIGI32_8	0x9898
> >
> > +#define PCI_VENDOR_ID_REDHAT_QUMRANET	0x1af4
> > +#define PCI_DEVICE_ID_VIRTIO_BLK	0x1001
> > diff --git a/src/post.c b/src/post.c
> > index 638b0f7..25535e2 100644
> > --- a/src/post.c
> > +++ b/src/post.c
> > @@ -23,6 +23,7 @@
> >  #include "smbios.h" // smbios_init
> >  #include "paravirt.h" // qemu_cfg_port_probe
> >  #include "ps2port.h" // ps2port_setup
> > +#include "virtio-blk.h" // virtio_blk_setup
> >
> > void
> >  __set_irq(int vector, void *loc)
> > @@ -184,6 +185,7 @@ init_hw(void)
> >      floppy_setup();
> >      ata_setup();
> >      ramdisk_setup();
> > virtio_blk_setup();
> >
> > }
> >
> > // Main setup code.
> > diff --git a/src/virtio-blk.c b/src/virtio-blk.c
> > new file mode 100644
> > index 0000000..a41c336
> > --- /dev/null
> > +++ b/src/virtio-blk.c
> > @@ -0,0 +1,155 @@
> > +// Virtio blovl boot support.
> > +//
> > +// Copyright (C) 2010 Red Hat Inc.
> > +//
> > +// Authors:
> > +//  Gleb Natapov
> > +//
> > +// This file may be distributed under the terms of the GNU LGPLv3 license.
> >
> > +#include "util.h" // dprintf
> > +#include "pci.h" // foreachpci
> > +#include "config.h" // CONFIG_*
> > +#include "virtio-pci.h"
> > +#include "virtio-blk.h"
> > +#include "disk.h"
> >
> > +struct virtiodrive_s {
> > struct drive_s drive;
> > struct vring_virtqueue *vq;
> > u16 ioaddr;
> >
> > +};
> >
> > +static int
> > +virtio_blk_read(struct disk_op_s *op)
> > +{
> > struct virtiodrive_s *vdrive_g =
> >    container_of(op->drive_g, struct virtiodrive_s, drive);
> > struct vring_virtqueue *vq = GET_GLOBAL(vdrive_g->vq);
> > struct virtio_blk_outhdr hdr = {
> >    .type = VIRTIO_BLK_T_IN,
> >    .ioprio = 0,
> >    .sector = op->lba,
> > };
> > u8 status = VIRTIO_BLK_S_UNSUPP;
> > struct vring_list sg[] = {
> >    {
> >        .addr	= MAKE_FLATPTR(GET_SEG(SS),&hdr),
> >        .length	= sizeof(hdr),
> >    },
> >    {
> >        .addr	= op->buf_fl,
> >        .length	= GET_GLOBAL(vdrive_g->drive.blksize) * op->count,
> >    },
> >    {
> >        .addr	= MAKE_FLATPTR(GET_SEG(SS),&status),
> >        .length	= sizeof(status),
> >    },
> > };
> > /* Add to virtqueue and kick host */
> > vring_add_buf(vq, sg, 1, 2, 0, 0);
> > vring_kick(GET_GLOBAL(vdrive_g->ioaddr), vq, 1);
> > /* Wait for reply */
> > while (!vring_more_used(vq))
> >    udelay(5);
> > /* Reclaim virtqueue element */
> > vring_get_buf(vq, NULL);
> > return status == VIRTIO_BLK_S_OK ? DISK_RET_SUCCESS : DISK_RET_EBADTRACK;
> >
> > +}
> >
> > +int
> > +process_virtio_op(struct disk_op_s *op)
> > +{
> > switch (op->command) {
> > case CMD_READ:
> >    return virtio_blk_read(op);
> > case CMD_FORMAT:
> > case CMD_WRITE:
> >    return DISK_RET_EWRITEPROTECT;
> > case CMD_RESET:
> > case CMD_ISREADY:
> > case CMD_VERIFY:
> > case CMD_SEEK:
> >    return DISK_RET_SUCCESS;
> > default:
> >    op->count = 0;
> >    return DISK_RET_EPARAM;
> > }
> >
> > +}
> >
> > +void
> > +virtio_blk_setup(void)
> > +{
> > ASSERT32FLAT();
> > if (! CONFIG_VIRTIO_BLK)
> >    return;
> > dprintf(3, "init virtio-blk\n");
> > int bdf, max;
> > u32 id = PCI_VENDOR_ID_REDHAT_QUMRANET | (PCI_DEVICE_ID_VIRTIO_BLK<<  16);
> > foreachpci(bdf, max) {
> >    u32 v = pci_config_readl(bdf, PCI_VENDOR_ID);
> >    if (v != id)
> >        continue;
> >    dprintf(3, "found virtio-blk at %x:%x\n", pci_bdf_to_bus(bdf),
> >            pci_bdf_to_dev(bdf));
> >    char *desc = malloc_tmphigh(MAXDESCSIZE);
> >    struct virtiodrive_s *vdrive_g = malloc_fseg(sizeof(*vdrive_g));
> >    struct vring_virtqueue *vq = malloc_low(sizeof(*vq));
> >    if (!vdrive_g || !desc || !vq) {
> >        warn_noalloc();
> >        return;
> >    }
> >    memset(vdrive_g, 0, sizeof(*vdrive_g));
> >    vdrive_g->drive.type = DTYPE_VIRTIO;
> >    vdrive_g->drive.cntl_id = bdf;
> >    vdrive_g->vq = vq;
> >    u16 ioaddr = pci_config_readl(bdf, PCI_BASE_ADDRESS_0)&
> >        PCI_BASE_ADDRESS_IO_MASK;
> >    vdrive_g->ioaddr = ioaddr;
> >    vp_reset(ioaddr);
> >    vp_set_status(ioaddr, VIRTIO_CONFIG_S_ACKNOWLEDGE |
> >                  VIRTIO_CONFIG_S_DRIVER );
> >    if (vp_find_vq(ioaddr, 0, vdrive_g->vq)<  0 ) {
> >        free(vdrive_g);
> >        free(desc);
> >        free(vq);
> >        dprintf(1, "fail to find vq for virtio-blk %x:%x\n",
> >                pci_bdf_to_bus (bdf), pci_bdf_to_dev(bdf));
> >        continue;
> >    }
> >    struct virtio_blk_config cfg;
> >    vp_get(ioaddr, 0,&cfg, sizeof(cfg));
> >    vdrive_g->drive.blksize = cfg.blk_size;
> >    vdrive_g->drive.sectors = cfg.capacity;
> >    dprintf(3, "virtio-blk %x:%x blksize=%d sectors=%u\n",
> >            pci_bdf_to_bus (bdf), pci_bdf_to_dev(bdf),
> >            vdrive_g->drive.blksize, (u32)vdrive_g->drive.sectors);
> >    vdrive_g->drive.pchs.cylinders = cfg.cylinders;
> >    vdrive_g->drive.pchs.heads = cfg.heads;
> >    vdrive_g->drive.pchs.spt = cfg.sectors;
> >    setup_translation(&vdrive_g->drive);
> >    add_bcv_internal(&vdrive_g->drive);
> >    snprintf(desc, MAXDESCSIZE, "Virtio disk PCI:%x:%x",
> >             pci_bdf_to_bus(bdf), pci_bdf_to_dev(bdf));
> >    vdrive_g->drive.desc = desc;
> >    vp_set_status(ioaddr, VIRTIO_CONFIG_S_ACKNOWLEDGE |
> >                  VIRTIO_CONFIG_S_DRIVER | VIRTIO_CONFIG_S_DRIVER_OK);
> > }
> >
> > +}
> >
> > diff --git a/src/virtio-blk.h b/src/virtio-blk.h
> > new file mode 100644
> > index 0000000..3369ea4
> > --- /dev/null
> > +++ b/src/virtio-blk.h
> > @@ -0,0 +1,40 @@
> > +#ifndef _VIRTIO_BLK_H
> > +#define _VIRTIO_BLK_H
> >
> > +struct virtio_blk_config
> > +{
> > u64 capacity;
> > u32 size_max;
> > u32 seg_max;
> > u16 cylinders;
> > u8 heads;
> > u8 sectors;
> > u32 blk_size;
> > u8 physical_block_exp;
> > u8 alignment_offset;
> > u16 min_io_size;
> > u32 opt_io_size;
> >
> > +} __attribute__((packed));
> >
> > +/* These two define direction. */
> > +#define VIRTIO_BLK_T_IN		0
> > +#define VIRTIO_BLK_T_OUT	1
> >
> > +/* This is the first element of the read scatter-gather list. */
> > +struct virtio_blk_outhdr {
> > /* VIRTIO_BLK_T* */
> > u32 type;
> > /* io priority. */
> > u32 ioprio;
> > /* Sector (ie. 512 byte offset) */
> > u64 sector;
> >
> > +};
> >
> > +#define VIRTIO_BLK_S_OK		0
> > +#define VIRTIO_BLK_S_IOERR	1
> > +#define VIRTIO_BLK_S_UNSUPP	2
> >
> > +int process_virtio_op(struct disk_op_s *op);
> > +void virtio_blk_setup(void);
> >
> > +#endif /* _VIRTIO_BLK_H */
> > diff --git a/src/virtio-pci.c b/src/virtio-pci.c
> > new file mode 100644
> > index 0000000..e171ea3
> > --- /dev/null
> > +++ b/src/virtio-pci.c
> > @@ -0,0 +1,67 @@
> > +/* virtio-pci.c - pci interface for virtio interface
> > (c) Copyright 2008 Bull S.A.S.
> > Author: Laurent Vivier
> > some parts from Linux Virtio PCI driver
> > Copyright IBM Corp. 2007
> > Authors: Anthony Liguori
> > Adopted for Seabios: Gleb Natapov
> > This work is licensed under the terms of the GNU LGPLv3
> > See the COPYING file in the top-level directory.
> > */
> >
> > +#include "virtio-ring.h"
> > +#include "virtio-pci.h"
> >
> > +int vp_find_vq(unsigned int ioaddr, int queue_index,
> >           struct vring_virtqueue *vq)
> >
> > +{
> > struct vring * vr =&vq->vring;
> > u16 num;
> > ASSERT32FLAT();
> > /* select the queue */
> > outw(queue_index, ioaddr + VIRTIO_PCI_QUEUE_SEL);
> > /* check if the queue is available */
> > num = inw(ioaddr + VIRTIO_PCI_QUEUE_NUM);
> > if (!num) {
> >   dprintf(1, "ERROR: queue size is 0\n");
> >   return -1;
> > }
> > if (num>  MAX_QUEUE_NUM) {
> >   dprintf(1, "ERROR: queue size %d>  %d\n", num, MAX_QUEUE_NUM);
> >   return -1;
> > }
> > /* check if the queue is already active */
> > if (inl(ioaddr + VIRTIO_PCI_QUEUE_PFN)) {
> >   dprintf(1, "ERROR: queue already active\n");
> >   return -1;
> > }
> > vq->queue_index = queue_index;
> > /* initialize the queue */
> > vring_init(vr, num, (unsigned char*)&vq->queue);
> > /* activate the queue
> > NOTE: vr->desc is initialized by vring_init()
> > */
> > outl((unsigned long)virt_to_phys(vr->desc)>>  PAGE_SHIFT,
> >    ioaddr + VIRTIO_PCI_QUEUE_PFN);
> > return num;
> >
> > +}
> > diff --git a/src/virtio-pci.h b/src/virtio-pci.h
> > new file mode 100644
> > index 0000000..6932036
> > --- /dev/null
> > +++ b/src/virtio-pci.h
> > @@ -0,0 +1,97 @@
> > +#ifndef _VIRTIO_PCI_H
> > +#define _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
> >
> > +/* The bit of the ISR which indicates a device configuration change. */
> > +#define VIRTIO_PCI_ISR_CONFIG           0x2
> >
> > +/* The remaining space is defined by each driver as the per-driver
> > configuration space */
> >
> > +#define VIRTIO_PCI_CONFIG               20
> >
> > +/* Virtio ABI version, this must match exactly */
> > +#define VIRTIO_PCI_ABI_VERSION          0
> >
> > +static inline u32 vp_get_features(unsigned int ioaddr)
> > +{
> > return inl(ioaddr + VIRTIO_PCI_HOST_FEATURES);
> >
> > +}
> >
> > +static inline void vp_set_features(unsigned int ioaddr, u32 features)
> > +{
> >    outl(features, ioaddr + VIRTIO_PCI_GUEST_FEATURES);
> >
> > +}
> >
> > +static inline void vp_get(unsigned int ioaddr, unsigned offset,
> >                 void *buf, unsigned len)
> >
> > +{
> > u8 *ptr = buf;
> > unsigned i;
> > for (i = 0; i<  len; i++)
> >       ptr[i] = inb(ioaddr + VIRTIO_PCI_CONFIG + offset + i);
> >
> > +}
> >
> > +static inline u8 vp_get_status(unsigned int ioaddr)
> > +{
> > return inb(ioaddr + VIRTIO_PCI_STATUS);
> >
> > +}
> >
> > +static inline void vp_set_status(unsigned int ioaddr, u8 status)
> > +{
> > if (status == 0)        /* reset */
> >       return;
> > outb(status, ioaddr + VIRTIO_PCI_STATUS);
> >
> > +}
> >
> > +static inline void vp_reset(unsigned int ioaddr)
> > +{
> > outb(0, ioaddr + VIRTIO_PCI_STATUS);
> > (void)inb(ioaddr + VIRTIO_PCI_ISR);
> >
> > +}
> >
> > +static inline void vp_notify(unsigned int ioaddr, int queue_index)
> > +{
> > outw(queue_index, ioaddr + VIRTIO_PCI_QUEUE_NOTIFY);
> >
> > +}
> >
> > +static inline void vp_del_vq(unsigned int ioaddr, int queue_index)
> > +{
> > /* select the queue */
> > outw(queue_index, ioaddr + VIRTIO_PCI_QUEUE_SEL);
> > /* deactivate the queue */
> > outl(0, ioaddr + VIRTIO_PCI_QUEUE_PFN);
> >
> > +}
> >
> > +int vp_find_vq(unsigned int ioaddr, int queue_index,
> >           struct vring_virtqueue *vq);
> >
> > +#endif /* _VIRTIO_PCI_H_ */
> > diff --git a/src/virtio-ring.c b/src/virtio-ring.c
> > new file mode 100644
> > index 0000000..f4a2efe
> > --- /dev/null
> > +++ b/src/virtio-ring.c
> > @@ -0,0 +1,152 @@
> > +/* virtio-pci.c - virtio ring management
> > (c) Copyright 2008 Bull S.A.S.
> > Author: Laurent Vivier
> > some parts from Linux Virtio Ring
> > Copyright Rusty Russell IBM Corporation 2007
> > Adopted for Seabios: Gleb Natapov
> > This work is licensed under the terms of the GNU LGPLv3
> > See the COPYING file in the top-level directory.
> > */
> >
> > +#include "virtio-ring.h"
> > +#include "virtio-pci.h"
> >
> > +#define BUG() do {                                      \
> >    dprintf(1, "BUG: failure at %s:%d/%s()!\n",     \
> >            __FILE__, __LINE__, __FUNCTION__);      \
> >            while(1);                               \
> >    } while (0)
> >
> > +#define BUG_ON(condition) do { if (condition) BUG(); } while (0)
> >
> > +/*
> > vring_more_used
> > is there some used buffers ?
> > */
> >
> > +int vring_more_used(struct vring_virtqueue *vq)
> > +{
> > struct vring_used *used = GET_FLATPTR(vq->vring.used);
> > wmb();
> > return GET_FLATPTR(vq->last_used_idx) != GET_FLATPTR(used->idx);
> >
> > +}
> >
> > +/*
> > vring_free
> > put at the begin of the free list the current desc[head]
> > */
> >
> > +void vring_detach(struct vring_virtqueue *vq, unsigned int head)
> > +{
> > struct vring *vr =&vq->vring;
> > struct vring_desc *desc = GET_FLATPTR(vr->desc);
> > unsigned int i;
> > /* find end of given descriptor */
> > i = head;
> > while (GET_FLATPTR(desc[i].flags)&  VRING_DESC_F_NEXT)
> >    i = GET_FLATPTR(desc[i].next);
> > /* link it with free list and point to it */
> > SET_FLATPTR(desc[i].next, GET_FLATPTR(vq->free_head));
> > wmb();
> > SET_FLATPTR(vq->free_head, head);
> >
> > +}
> >
> > +/*
> > vring_get_buf
> > get a buffer from the used list
> > */
> >
> > +int vring_get_buf(struct vring_virtqueue *vq, unsigned int *len)
> > +{
> > struct vring *vr =&vq->vring;
> > struct vring_used_elem *elem;
> > struct vring_used *used = GET_FLATPTR(vq->vring.used);
> > u32 id;
> > int ret;
> >
> > +//    BUG_ON(!vring_more_used(vq));
> > elem =&used->ring[GET_FLATPTR(vq->last_used_idx) % GET_FLATPTR(vr->num)];
> > wmb();
> > id = GET_FLATPTR(elem->id);
> > if (len != NULL)
> >    *len = GET_FLATPTR(elem->len);
> > ret = GET_FLATPTR(vq->vdata[id]);
> > vring_detach(vq, id);
> > SET_FLATPTR(vq->last_used_idx, GET_FLATPTR(vq->last_used_idx) + 1);
> > return ret;
> >
> > +}
> >
> > +void vring_add_buf(struct vring_virtqueue *vq,
> >               struct vring_list list[],
> >               unsigned int out, unsigned int in,
> >               int index, int num_added)
> >
> > +{
> > struct vring *vr =&vq->vring;
> > int i, av, head, prev;
> > struct vring_desc *desc = GET_FLATPTR(vr->desc);
> > struct vring_avail *avail = GET_FLATPTR(vr->avail);
> > BUG_ON(out + in == 0);
> > prev = 0;
> > head = GET_FLATPTR(vq->free_head);
> > for (i = head; out; i = GET_FLATPTR(desc[i].next), out--) {
> >    SET_FLATPTR(desc[i].flags, VRING_DESC_F_NEXT);
> >    SET_FLATPTR(desc[i].addr, (u64)virt_to_phys(list->addr));
> >    SET_FLATPTR(desc[i].len, list->length);
> >    prev = i;
> >    list++;
> > }
> > for ( ; in; i = GET_FLATPTR(desc[i].next), in--) {
> >    SET_FLATPTR(desc[i].flags, VRING_DESC_F_NEXT|VRING_DESC_F_WRITE);
> >    SET_FLATPTR(desc[i].addr, (u64)virt_to_phys(list->addr));
> >    SET_FLATPTR(desc[i].len, list->length);
> >    prev = i;
> >    list++;
> > }
> > SET_FLATPTR(desc[prev].flags,
> >            GET_FLATPTR(desc[prev].flags)&  ~VRING_DESC_F_NEXT);
> > SET_FLATPTR(vq->free_head, i);
> > SET_FLATPTR(vq->vdata[head], index);
> > av = (GET_FLATPTR(avail->idx) + num_added) % GET_FLATPTR(vr->num);
> > SET_FLATPTR(avail->ring[av], head);
> > wmb();
> >
> > +}
> >
> > +void vring_kick(unsigned int ioaddr, struct vring_virtqueue *vq, int num_added)
> > +{
> > struct vring *vr =&vq->vring;
> > struct vring_avail *avail = GET_FLATPTR(vr->avail);
> > struct vring_used *used = GET_FLATPTR(vq->vring.used);
> > wmb();
> > SET_FLATPTR(avail->idx, GET_FLATPTR(avail->idx) + num_added);
> > mb();
> > if (!(GET_FLATPTR(used->flags)&  VRING_USED_F_NO_NOTIFY))
> >    vp_notify(ioaddr, GET_FLATPTR(vq->queue_index));
> >
> > +}
> > diff --git a/src/virtio-ring.h b/src/virtio-ring.h
> > new file mode 100644
> > index 0000000..b97d572
> > --- /dev/null
> > +++ b/src/virtio-ring.h
> > @@ -0,0 +1,125 @@
> > +#ifndef _VIRTIO_RING_H
> > +#define _VIRTIO_RING_H
> >
> > +#define PAGE_SHIFT 12
> > +#define PAGE_MASK  (PAGE_SIZE-1)
> >
> > +#define virt_to_phys(v) (unsigned long)(v)
> > +#define phys_to_virt(p) (void*)(p)
> > +#define wmb() barrier()
> > +#define mb() barrier()
> >
> > +/* 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
> >
> > +#define MAX_QUEUE_NUM      (128)
> >
> > +#define VRING_DESC_F_NEXT  1
> > +#define VRING_DESC_F_WRITE 2
> >
> > +#define VRING_AVAIL_F_NO_INTERRUPT 1
> >
> > +#define VRING_USED_F_NO_NOTIFY     1
> >
> > +struct vring_desc
> > +{
> > u64 addr;
> > u32 len;
> > u16 flags;
> > u16 next;
> >
> > +};
> >
> > +struct vring_avail
> > +{
> > u16 flags;
> > u16 idx;
> > u16 ring[0];
> >
> > +};
> >
> > +struct vring_used_elem
> > +{
> > u32 id;
> > u32 len;
> >
> > +};
> >
> > +struct vring_used
> > +{
> > u16 flags;
> > u16 idx;
> > struct vring_used_elem ring[];
> >
> > +};
> >
> > +struct vring {
> > unsigned int num;
> > struct vring_desc *desc;
> > struct vring_avail *avail;
> > struct vring_used *used;
> >
> > +};
> >
> > +#define vring_size(num) \
> > (((((sizeof(struct vring_desc) * num) + \
> >  (sizeof(struct vring_avail) + sizeof(u16) * num)) \
> >     + PAGE_MASK)&  ~PAGE_MASK) + \
> >     (sizeof(struct vring_used) + sizeof(struct vring_used_elem) * num))
> >
> > +typedef unsigned char virtio_queue_t[PAGE_MASK + vring_size(MAX_QUEUE_NUM)];
> >
> > +struct vring_virtqueue {
> > virtio_queue_t queue;
> > struct vring vring;
> > u16 free_head;
> > u16 last_used_idx;
> > u16 vdata[MAX_QUEUE_NUM];
> > /* PCI */
> > int queue_index;
> >
> > +};
> >
> > +struct vring_list {
> > char *addr;
> > unsigned int length;
> >
> > +};
> >
> > +static inline void vring_init(struct vring *vr,
> >                     unsigned int num, unsigned char *queue)
> >
> > +{
> > unsigned int i;
> > unsigned long pa;
> > ASSERT32FLAT();
> > vr->num = num;
> > /* physical address of desc must be page aligned */
> > pa = virt_to_phys(queue);
> > pa = (pa + PAGE_MASK)&  ~PAGE_MASK;
> > vr->desc = phys_to_virt(pa);
> > vr->avail = (struct vring_avail *)&vr->desc[num];
> > /* physical address of used must be page aligned */
> > pa = virt_to_phys(&vr->avail->ring[num]);
> > pa = (pa + PAGE_MASK)&  ~PAGE_MASK;
> > vr->used = phys_to_virt(pa);
> > for (i = 0; i<  num - 1; i++)
> >       vr->desc[i].next = i + 1;
> > vr->desc[i].next = 0;
> >
> > +}
> >
> > +int vring_more_used(struct vring_virtqueue *vq);
> > +void vring_detach(struct vring_virtqueue *vq, unsigned int head);
> > +int vring_get_buf(struct vring_virtqueue *vq, unsigned int *len);
> > +void vring_add_buf(struct vring_virtqueue *vq, struct vring_list list[],
> >               unsigned int out, unsigned int in,
> >               int index, int num_added);
> >
> > +void vring_kick(unsigned int ioaddr, struct vring_virtqueue *vq, int num_added);
> >
> > +#endif /* _VIRTIO_RING_H_ */