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hw/xen: automatically assign device index to block devices

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There's no need to force the user to assign a vdev. We can automatically
assign one, starting at xvda and searching until we find the first disk
name that's unused.

This means we can now allow '-drive if=xen,file=xxx' to work without an
explicit separate -driver argument, just like if=virtio.

Rip out the legacy handling from the xenpv machine, which was scribbling
over any disks configured by the toolstack, and didn't work with anything
but raw images.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Paul Durrant <paul@xen.org>
This commit is contained in:
David Woodhouse 2023-10-16 13:01:39 +01:00
parent d388c9f53b
commit d3256f88d9
5 changed files with 125 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
blockdev.c
View File

@ -255,13 +255,13 @@ void drive_check_orphaned(void)
* Ignore default drives, because we create certain default
* drives unconditionally, then leave them unclaimed. Not the
* users fault.
* Ignore IF_VIRTIO, because it gets desugared into -device,
* so we can leave failing to -device.
* Ignore IF_VIRTIO or IF_XEN, because it gets desugared into
* -device, so we can leave failing to -device.
* Ignore IF_NONE, because leaving unclaimed IF_NONE remains
* available for device_add is a feature.
*/
if (dinfo->is_default || dinfo->type == IF_VIRTIO
|| dinfo->type == IF_NONE) {
|| dinfo->type == IF_XEN || dinfo->type == IF_NONE) {
continue;
}
if (!blk_get_attached_dev(blk)) {
@ -977,6 +977,15 @@ DriveInfo *drive_new(QemuOpts *all_opts, BlockInterfaceType block_default_type,
qemu_opt_set(devopts, "driver", "virtio-blk", &error_abort);
qemu_opt_set(devopts, "drive", qdict_get_str(bs_opts, "id"),
&error_abort);
} else if (type == IF_XEN) {
QemuOpts *devopts;
devopts = qemu_opts_create(qemu_find_opts("device"), NULL, 0,
&error_abort);
qemu_opt_set(devopts, "driver",
(media == MEDIA_CDROM) ? "xen-cdrom" : "xen-disk",
&error_abort);
qemu_opt_set(devopts, "drive", qdict_get_str(bs_opts, "id"),
&error_abort);
}
filename = qemu_opt_get(legacy_opts, "file");

118
hw/block/xen-block.c
View File

@ -27,13 +27,119 @@
#include "sysemu/block-backend.h"
#include "sysemu/iothread.h"
#include "dataplane/xen-block.h"
#include "hw/xen/interface/io/xs_wire.h"
#include "trace.h"
#define XVDA_MAJOR 202
#define XVDQ_MAJOR (1 << 20)
#define XVDBGQCV_MAJOR ((1 << 21) - 1)
#define HDA_MAJOR 3
#define HDC_MAJOR 22
#define SDA_MAJOR 8
static int vdev_to_diskno(unsigned int vdev_nr)
{
switch (vdev_nr >> 8) {
case XVDA_MAJOR:
case SDA_MAJOR:
return (vdev_nr >> 4) & 0x15;
case HDA_MAJOR:
return (vdev_nr >> 6) & 1;
case HDC_MAJOR:
return ((vdev_nr >> 6) & 1) + 2;
case XVDQ_MAJOR ... XVDBGQCV_MAJOR:
return (vdev_nr >> 8) & 0xfffff;
default:
return -1;
}
}
#define MAX_AUTO_VDEV 4096
/*
* Find a free device name in the xvda → xvdfan range and set it in
* blockdev->props.vdev. Our definition of "free" is that there must
* be no other disk or partition with the same disk number.
*
* You are technically permitted to have all of hda, hda1, sda, sda1,
* xvda and xvda1 as *separate* PV block devices with separate backing
* stores. That doesn't make it a good idea. This code will skip xvda
* if *any* of those "conflicting" devices already exists.
*
* The limit of xvdfan (disk 4095) is fairly arbitrary just to avoid a
* stupidly sized bitmap, but Linux as of v6.6 doesn't support anything
* higher than that anyway.
*/
static bool xen_block_find_free_vdev(XenBlockDevice *blockdev, Error **errp)
{
XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(blockdev)));
unsigned long used_devs[BITS_TO_LONGS(MAX_AUTO_VDEV)];
XenBlockVdev *vdev = &blockdev->props.vdev;
char fe_path[XENSTORE_ABS_PATH_MAX + 1];
char **existing_frontends;
unsigned int nr_existing = 0;
unsigned int vdev_nr;
int i, disk = 0;
snprintf(fe_path, sizeof(fe_path), "/local/domain/%u/device/vbd",
blockdev->xendev.frontend_id);
existing_frontends = qemu_xen_xs_directory(xenbus->xsh, XBT_NULL, fe_path,
&nr_existing);
if (!existing_frontends && errno != ENOENT) {
error_setg_errno(errp, errno, "cannot read %s", fe_path);
return false;
}
memset(used_devs, 0, sizeof(used_devs));
for (i = 0; i < nr_existing; i++) {
if (qemu_strtoui(existing_frontends[i], NULL, 10, &vdev_nr)) {
free(existing_frontends[i]);
continue;
}
free(existing_frontends[i]);
disk = vdev_to_diskno(vdev_nr);
if (disk < 0 || disk >= MAX_AUTO_VDEV) {
continue;
}
set_bit(disk, used_devs);
}
free(existing_frontends);
disk = find_first_zero_bit(used_devs, MAX_AUTO_VDEV);
if (disk == MAX_AUTO_VDEV) {
error_setg(errp, "cannot find device vdev for block device");
return false;
}
vdev->type = XEN_BLOCK_VDEV_TYPE_XVD;
vdev->partition = 0;
vdev->disk = disk;
if (disk < (1 << 4)) {
vdev->number = (XVDA_MAJOR << 8) | (disk << 4);
} else {
vdev->number = (XVDQ_MAJOR << 8) | (disk << 8);
}
return true;
}
static char *xen_block_get_name(XenDevice *xendev, Error **errp)
{
XenBlockDevice *blockdev = XEN_BLOCK_DEVICE(xendev);
XenBlockVdev *vdev = &blockdev->props.vdev;
if (vdev->type == XEN_BLOCK_VDEV_TYPE_INVALID &&
!xen_block_find_free_vdev(blockdev, errp)) {
return NULL;
}
return g_strdup_printf("%lu", vdev->number);
}
@ -482,10 +588,10 @@ static void xen_block_set_vdev(Object *obj, Visitor *v, const char *name,
case XEN_BLOCK_VDEV_TYPE_DP:
case XEN_BLOCK_VDEV_TYPE_XVD:
if (vdev->disk < (1 << 4) && vdev->partition < (1 << 4)) {
vdev->number = (202 << 8) | (vdev->disk << 4) |
vdev->number = (XVDA_MAJOR << 8) | (vdev->disk << 4) |
vdev->partition;
} else if (vdev->disk < (1 << 20) && vdev->partition < (1 << 8)) {
vdev->number = (1 << 28) | (vdev->disk << 8) |
vdev->number = (XVDQ_MAJOR << 8) | (vdev->disk << 8) |
vdev->partition;
} else {
goto invalid;
@ -495,10 +601,11 @@ static void xen_block_set_vdev(Object *obj, Visitor *v, const char *name,
case XEN_BLOCK_VDEV_TYPE_HD:
if ((vdev->disk == 0 || vdev->disk == 1) &&
vdev->partition < (1 << 6)) {
vdev->number = (3 << 8) | (vdev->disk << 6) | vdev->partition;
vdev->number = (HDA_MAJOR << 8) | (vdev->disk << 6) |
vdev->partition;
} else if ((vdev->disk == 2 || vdev->disk == 3) &&
vdev->partition < (1 << 6)) {
vdev->number = (22 << 8) | ((vdev->disk - 2) << 6) |
vdev->number = (HDC_MAJOR << 8) | ((vdev->disk - 2) << 6) |
vdev->partition;
} else {
goto invalid;
@ -507,7 +614,8 @@ static void xen_block_set_vdev(Object *obj, Visitor *v, const char *name,
case XEN_BLOCK_VDEV_TYPE_SD:
if (vdev->disk < (1 << 4) && vdev->partition < (1 << 4)) {
vdev->number = (8 << 8) | (vdev->disk << 4) | vdev->partition;
vdev->number = (SDA_MAJOR << 8) | (vdev->disk << 4) |
vdev->partition;
} else {
goto invalid;
}

28
hw/xen/xen_devconfig.c
View File

@ -46,34 +46,6 @@ static int xen_config_dev_all(char *fe, char *be)
/* ------------------------------------------------------------- */
int xen_config_dev_blk(DriveInfo *disk)
{
char fe[256], be[256], device_name[32];
int vdev = 202 * 256 + 16 * disk->unit;
int cdrom = disk->media_cd;
const char *devtype = cdrom ? "cdrom" : "disk";
const char *mode = cdrom ? "r" : "w";
const char *filename = qemu_opt_get(disk->opts, "file");
snprintf(device_name, sizeof(device_name), "xvd%c", 'a' + disk->unit);
xen_pv_printf(NULL, 1, "config disk %d [%s]: %s\n",
disk->unit, device_name, filename);
xen_config_dev_dirs("vbd", "qdisk", vdev, fe, be, sizeof(fe));
/* frontend */
xenstore_write_int(fe, "virtual-device", vdev);
xenstore_write_str(fe, "device-type", devtype);
/* backend */
xenstore_write_str(be, "dev", device_name);
xenstore_write_str(be, "type", "file");
xenstore_write_str(be, "params", filename);
xenstore_write_str(be, "mode", mode);
/* common stuff */
return xen_config_dev_all(fe, be);
}
int xen_config_dev_nic(NICInfo *nic)
{
char fe[256], be[256];

9
hw/xenpv/xen_machine_pv.c
View File

@ -32,7 +32,6 @@
static void xen_init_pv(MachineState *machine)
{
DriveInfo *dinfo;
int i;
setup_xen_backend_ops();
@ -64,14 +63,6 @@ static void xen_init_pv(MachineState *machine)
vga_interface_created = true;
}
/* configure disks */
for (i = 0; i < 16; i++) {
dinfo = drive_get(IF_XEN, 0, i);
if (!dinfo)
continue;
xen_config_dev_blk(dinfo);
}
/* configure nics */
for (i = 0; i < nb_nics; i++) {
if (!nd_table[i].model || 0 != strcmp(nd_table[i].model, "xen"))

1
include/hw/xen/xen-legacy-backend.h
View File

@ -81,7 +81,6 @@ extern struct XenDevOps xen_usb_ops; /* xen-usb.c */
/* configuration (aka xenbus setup) */
void xen_config_cleanup(void);
int xen_config_dev_blk(DriveInfo *disk);
int xen_config_dev_nic(NICInfo *nic);
int xen_config_dev_vfb(int vdev, const char *type);
int xen_config_dev_vkbd(int vdev);