Re: [PATCH] Report stringified errno in VFIO related errors

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On Fri, Feb 14, 2020 at 10:20 AM Michal Privoznik <mprivozn@redhat.com> wrote:
> On 2/14/20 9:47 AM, Michal Privoznik wrote:
> > In a few places we report errno formatted as a negative integer.
> > This is not as user friendly as it can be. Use strerror() and/or
> > error_setg_errno() instead.
> >
> > Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
> > ---
> >   hw/vfio/common.c    | 2 +-
> >   util/vfio-helpers.c | 6 +++---
> >   2 files changed, 4 insertions(+), 4 deletions(-)
> >
>
> BTW the reason I've noticed these is because I'm seeing some errors when
> assigning my NVMe disk to qemu. This is the full command line:
>
>
> /home/zippy/work/qemu/qemu.git/x86_64-softmmu/qemu-system-x86_64 \
> -name guest=fedora,debug-threads=on \
> -S \
> -object
> secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-2-fedora/master-key.aes
> \
> -machine pc-i440fx-4.1,accel=kvm,usb=off,dump-guest-core=off \
> -cpu host \
> -m size=4194304k,slots=16,maxmem=1099511627776k \
> -overcommit mem-lock=off \
> -smp 4,sockets=1,dies=1,cores=2,threads=2 \
> -object iothread,id=iothread1 \
> -object iothread,id=iothread2 \
> -object iothread,id=iothread3 \
> -object iothread,id=iothread4 \
> -mem-prealloc \
> -mem-path /hugepages2M/libvirt/qemu/2-fedora \
> -numa node,nodeid=0,cpus=0,mem=4096 \
> -uuid 63840878-0deb-4095-97e6-fc444d9bc9fa \
> -no-user-config \
> -nodefaults \
> -chardev socket,id=charmonitor,fd=31,server,nowait \
> -mon chardev=charmonitor,id=monitor,mode=control \
> -rtc base=utc \
> -no-shutdown \
> -global PIIX4_PM.disable_s3=0 \
> -global PIIX4_PM.disable_s4=0 \
> -boot menu=on,strict=on \
> -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \
> -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x4 \
> -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 \
> -blockdev
> '{"driver":"file","filename":"/var/lib/libvirt/images/fedora.qcow2","node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"}'
> \
> -blockdev
> '{"node-name":"libvirt-2-format","read-only":false,"discard":"unmap","driver":"qcow2","file":"libvirt-2-storage","backing":null}'
> \
> -device
> scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,device_id=drive-scsi0-0-0-0,drive=libvirt-2-format,id=scsi0-0-0-0,bootindex=1
> \
> -blockdev
> '{"driver":"nvme","device":"0000:02:00.0","namespace":1,"node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}'
> \
> -blockdev
> '{"node-name":"libvirt-1-format","read-only":false,"driver":"raw","file":"libvirt-1-storage"}'
> \
> -device
> virtio-blk-pci,scsi=off,bus=pci.0,addr=0x6,drive=libvirt-1-format,id=virtio-disk0
> \
> -netdev tap,fd=33,id=hostnet0,vhost=on,vhostfd=34 \
> -device
> virtio-net-pci,host_mtu=9000,netdev=hostnet0,id=net0,mac=52:54:00:a4:6f:91,bus=pci.0,addr=0x3
> \
> -chardev pty,id=charserial0 \
> -device isa-serial,chardev=charserial0,id=serial0 \
> -chardev socket,id=charchannel0,fd=35,server,nowait \
> -device
> virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0
> \
> -spice port=5900,addr=0.0.0.0,disable-ticketing,seamless-migration=on \
> -device virtio-vga,id=video0,virgl=on,max_outputs=1,bus=pci.0,addr=0x2 \
> -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 \
> -sandbox
> on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
> -msg timestamp=on
>
> And these are the errors I see:
>
> 2020-02-14T09:06:18.183167Z qemu-system-x86_64: VFIO_MAP_DMA failed:
> Invalid argument
> 2020-02-14T09:10:49.753767Z qemu-system-x86_64: VFIO_MAP_DMA failed:
> Cannot allocate memory
> 2020-02-14T09:11:04.530344Z qemu-system-x86_64: VFIO_MAP_DMA failed: No
> space left on device
> 2020-02-14T09:11:04.531087Z qemu-system-x86_64: VFIO_MAP_DMA failed: No
> space left on device
> 2020-02-14T09:11:04.531230Z qemu-system-x86_64: VFIO_MAP_DMA failed: No
> space left on device
>
>
> I'm doing nothing with the disk inside the guest, but:
>
>    # dd if=/dev/vda of=/dev/null status=progress
>
> (the disk appears as /dev/vda in the guest). Surprisingly, I do not see
> these errors when I use the traditional PCI assignment (-device
> vfio-pci). My versions of kernel and qemu:
>
> moe ~ # uname -r
> 5.4.15-gentoo
> moe ~ # /home/zippy/work/qemu/qemu.git/x86_64-softmmu/qemu-system-x86_64
> --version
> QEMU emulator version 4.2.50 (v4.2.0-1439-g5d6542bea7-dirty)
> Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers
>
> Do you guys want me to file a bug?

As you already have all the information, and it is a simple
copy/paste, I'd say "yes"