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Re: [RFC 0/5] hmp, qmp: Add some commands to introspect virtio devices
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [RFC 0/5] hmp, qmp: Add some commands to introspect virtio devices |
Date: |
Thu, 2 Apr 2020 16:23:45 +0100 |
User-agent: |
Mutt/1.13.4 (2020-02-15) |
* Marc-André Lureau (address@hidden) wrote:
> Hi
>
> On Thu, Apr 2, 2020 at 12:03 PM Laurent Vivier <address@hidden> wrote:
> >
> > This series introduces new QMP/HMP commands to dump the status
> > of a a virtio device at different levels.
>
> Looks nice, but my feeling is that we are growing qemu with debugging
> facilities in general with HMP/QMP.
>
> If this is only for debugging purposes, why don't we compile it only
> when --enable-debug?
>
> A guest that would need to be debugged could have its state loaded in
> a debug version of qemu.
>
> Alternatively, I think most of the data you provide here could
> probably be introspected via gdb scripts.
>
> Just some thoughts
I kind of agree, but virtio is bread-and-butter, so having it available
all the time isn't a bad idea; however having said that hte same
argument would be for why having gdb scripts to examine your virtio
queues would be useful if you're dealing with a core.
Dave
>
> >
> > 1. Main command
> >
> > HMP Only:
> >
> > virtio [subcommand]
> >
> > Example:
> >
> > List all sub-commands:
> >
> > (qemu) virtio
> > virtio query -- List all available virtio devices
> > virtio status path -- Display status of a given virtio device
> > virtio queue-status path queue -- Display status of a given virtio queue
> > virtio queue-element path queue [index] -- Display element of a given
> > virtio queue
> >
> > 2. List available virtio devices in the machine
> >
> > HMP Form:
> >
> > virtio query
> >
> > Example:
> >
> > (qemu) virtio query
> > /machine/peripheral-anon/device[3]/virtio-backend [virtio-net]
> > /machine/peripheral-anon/device[1]/virtio-backend [virtio-serial]
> > /machine/peripheral-anon/device[0]/virtio-backend [virtio-blk]
> >
> > QMP Form:
> >
> > { 'command': 'query-virtio', 'returns': ['VirtioInfo'] }
> >
> > Example:
> >
> > -> { "execute": "query-virtio" }
> > <- { "return": [
> > {
> > "path": "/machine/peripheral-anon/device[3]/virtio-backend",
> > "type": "virtio-net"
> > },
> > {
> > "path": "/machine/peripheral-anon/device[1]/virtio-backend",
> > "type": "virtio-serial"
> > },
> > {
> > "path": "/machine/peripheral-anon/device[0]/virtio-backend",
> > "type": "virtio-blk"
> > }
> > ]
> > }
> >
> > 3. Display status of a given virtio device
> >
> > HMP Form:
> >
> > virtio status <path>
> >
> > Example:
> >
> > (qemu) virtio status /machine/peripheral-anon/device[3]/virtio-backend
> > /machine/peripheral-anon/device[3]/virtio-backend:
> > Device Id: 1
> > Guest features: 0x0000000130afffa7
> > Host features: 0x0000000179bfffe7
> > Backend features: 0x0000000000000000
> > Endianness: little
> > VirtQueues: 3
> >
> > QMP Form:
> >
> > { 'command': 'virtio-status',
> > 'data': { 'path': 'str' },
> > 'returns': 'VirtioStatus'
> > }
> >
> > Example:
> >
> > -> { "execute": "virtio-status",
> > "arguments": {
> > "path": "/machine/peripheral-anon/device[3]/virtio-backend"
> > }
> > }
> > <- { "return": {
> > "backend_features": 0,
> > "guest_features": 5111807911,
> > "num_vqs": 3,
> > "host_features": 6337593319,
> > "device_endian": "little",
> > "device_id": 1
> > }
> > }
> >
> > 4. Display status of a given virtio queue
> >
> > HMP Form:
> >
> > virtio queue-status <path> <queue>
> >
> > Example:
> >
> > (qemu) virtio queue-status
> > /machine/peripheral-anon/device[3]/virtio-backend 0
> > /machine/peripheral-anon/device[3]/virtio-backend:
> > index: 0
> > inuse: 0
> > last_avail_idx: 61
> > shadow_avail_idx: 292
> > signalled_used: 61
> > signalled_used_valid: 1
> > VRing:
> > num: 256
> > num_default: 256
> > align: 4096
> > desc: 0x000000006c352000
> > avail: 0x000000006c353000
> > used: 0x000000006c353240
> >
> > QMP Form:
> >
> > { 'command': 'virtio-queue-status',
> > 'data': { 'path': 'str', 'queue': 'uint16' },
> > 'returns': 'VirtQueueStatus'
> > }
> >
> > Example:
> >
> > -> { "execute": "virtio-queue-status",
> > "arguments": {
> > "path": "/machine/peripheral-anon/device[3]/virtio-backend",
> > "queue": 0
> > }
> > }
> > <- { "return": {
> > "signalled_used": 373,
> > "inuse": 0,
> > "vring_desc": 864411648,
> > "vring_num_default": 256,
> > "signalled_used_valid": 1,
> > "vring_avail": 864415744,
> > "last_avail_idx": 373,
> > "queue_index": 0,
> > "vring_used": 864416320,
> > "shadow_avail_idx": 619,
> > "used_idx": 373,
> > "vring_num": 256,
> > "vring_align": 4096
> > }
> > }
> >
> > 5. Display element of a given virtio queue
> >
> > HMP Form:
> >
> > virtio queue-element <path> <queue> [index]
> >
> > Example:
> >
> > Dump the information of the head element of the first queue of
> > the first virtio device::
> >
> > (qemu) virtio
> > queue-element/machine/peripheral-anon/device[3]/virtio-backend 0
> > index: 67
> > ndescs: 1
> > descs: addr 0x6fe69800 len 1536 (write-only)
> >
> > (qemu) xp/128bx 0x6fe69800
> > 000000006fe69800: 0x02 0x00 0x00 0x00 0x00 0x00 0x00 0x00
> > 000000006fe69808: 0x00 0x00 0x01 0x00 0x52 0x54 0x00 0x12
> > 000000006fe69810: 0x34 0x56 0x52 0x54 0x00 0x09 0x51 0xde
> > 000000006fe69818: 0x08 0x00 0x45 0x00 0x00 0x4c 0x8f 0x32
> >
> > device[3] is a virtio-net device and we can see in the element buffer
> > the
> > MAC address of the card::
> >
> > [root@localhost ~]# ip link show ens4
> > 2: ens4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel
> > state UP m0
> > link/ether 52:54:00:12:34:56 brd ff:ff:ff:ff:ff:ff
> >
> > and the MAC address of the gateway::
> >
> > [root@localhost ~]# arp -a
> > _gateway (192.168.122.1) at 52:54:00:09:51:de [ether] on ens4
> >
> > QMP Form:
> >
> > { 'command': 'virtio-queue-element',
> > 'data': { 'path': 'str', 'queue': 'uint16', '*index': 'uint16' },
> > 'returns': 'VirtioQueueElement'
> > }
> >
> > Example:
> >
> > -> { "execute": "virtio-queue-element",
> > "arguments": {
> > "path": "/machine/peripheral-anon/device[3]/virtio-backend",
> > "queue": 0
> > }
> > }
> > -> { "return": {
> > "index": 109,
> > "len": 0,
> > "ndescs": 1,
> > "descs": [
> > { "flags": 2, "len": 2048, "addr": 853145600 }
> > ]
> > }
> > }
> >
> > Laurent Vivier (5):
> > qmp: add QMP command query-virtio
> > qmp: add QMP command virtio-status
> > qmp: add QMP command virtio-queue-status
> > qmp: add QMP command virtio-queue-element
> > hmp: add virtio commands
> >
> > Makefile | 2 +-
> > Makefile.target | 7 +-
> > docs/system/monitor.rst | 2 +
> > hmp-commands-virtio.hx | 148 ++++++++++++++++++
> > hmp-commands.hx | 10 ++
> > hw/virtio/Makefile.objs | 2 +
> > hw/virtio/virtio-stub.c | 32 ++++
> > hw/virtio/virtio.c | 313 +++++++++++++++++++++++++++++++++++++
> > include/hw/virtio/virtio.h | 1 +
> > include/monitor/hmp.h | 4 +
> > monitor/misc.c | 17 ++
> > qapi/Makefile.objs | 2 +-
> > qapi/qapi-schema.json | 1 +
> > qapi/virtio.json | 302 +++++++++++++++++++++++++++++++++++
> > tests/qtest/qmp-cmd-test.c | 1 +
> > 15 files changed, 840 insertions(+), 4 deletions(-)
> > create mode 100644 hmp-commands-virtio.hx
> > create mode 100644 hw/virtio/virtio-stub.c
> > create mode 100644 qapi/virtio.json
> >
> > --
> > 2.25.1
> >
> >
>
>
> --
> Marc-André Lureau
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [RFC 2/5] qmp: add QMP command virtio-status, (continued)
- [RFC 2/5] qmp: add QMP command virtio-status, Laurent Vivier, 2020/04/02
- [RFC 3/5] qmp: add QMP command virtio-queue-status, Laurent Vivier, 2020/04/02
- [RFC 4/5] qmp: add QMP command virtio-queue-element, Laurent Vivier, 2020/04/02
- [RFC 5/5] hmp: add virtio commands, Laurent Vivier, 2020/04/02
- Re: [RFC 0/5] hmp, qmp: Add some commands to introspect virtio devices, Marc-André Lureau, 2020/04/02
- Re: [RFC 0/5] hmp, qmp: Add some commands to introspect virtio devices,
Dr. David Alan Gilbert <=