[libvirt-users] virsh not detecting hugepage mount; disabled by config?

[Martin Kletzander]

On Tue, Dec 13, 2016 at 11:05:11PM +0100, Manuel Ullmann wrote:
>Hi,
>
>I’m struggling with virsh not detecting my hugepage mount.
>
>I have the following kernel command line:
>BOOT_IMAGE=/vmlinuz-4.8.13-gentoo root=/dev/mapper/gensd-gentoo ro quiet
>splash intel_iommu=on video=efifb:off,vesafb:off,simplefb:off
>splash=verbose,theme:livedvd-aurora kvm.ignore_msrs=1
>transparent_hugepage=never hugepages=3072 softlevel=qemuvm
>
>My startup script outputs the following:
>hugetlbfs /var/lib/hugetlbfs hugetlbfs
>rw,relatime,pagesize=2097152,uid=77,gid=77,mode=0770 0 0
>[2016.12.13 22:22:50 virsh 2808] ERROR Failed to start domain win10
>[2016.12.13 22:22:50 virsh 2808] ERROR internal error: hugetlbfs
>filesystem is not mounted or disabled by administrator config
>virsh was unsuccessful
>
>So hugetlbfs is definitively mounted, but virsh does either not detect
>it or some magical option, that I’ve not found in a day searching for
>it, disables it (the documentation could explain that better). Since the
>Ubuntu guys refer to the KVM_HUGEPAGES environment, I tried adding it to
>start-stop-daemon environment, but it seems non-relevant. 77 is the qemu
>user id, but I’m quite sure the permission issues were excluded (tried
>root permissions as well). Besides I had permission errors occasionally
>occasionally and don’t have them anymore. If you could provide a hint to
>the magical administrator configuration option, that would be helpful.

Nothing magical about that.  If you have no hugepages configured in
qemu.conf, libvirtd will *try* to find all the mounts if running as
root.  The only thing is that in the error message "or" should be
changed to "and", I guess.

>Tried hugeadm as well, pointing the config to the correct destination.
>
>Thanks in advance,
>Manuel
>
>PS:
>The virsh script reads like this:
>#!/bin/sh
>cmdline="$(cat /proc/cmdline)"
>if [[ "${cmdline##* }" == "softlevel=qemuvm" ]]; then
>    mount -o rw,relatime,pagesize=2097152,uid=77,gid=77,mode=0770 -t
>hugetlbfs hugetlbfs /var/lib/hugetlbfs

If libvirtd starts before this ^^

>    sysctl kernel.shmmax=6442450944
>    cat /proc/mounts | grep hugetlb >> /var/log/virsh.log
>    sed -i -e '/^hugetlb/{s/^/\#/}' /etc/libvirt/qemu.conf

or this ^^ is done, then the settings are not reflected.  That's the
only thing I could glean from the quick look.

I bet adding 'service libvirtd restart' here helps.

>    counter=0
>    while [ "${counter}" -lt 10 && ! -S /var/run/libvirt/libvirt-sock ]; do
>    sleep 1
>    counter=$(( ++counter ))
>    done
>    if [ $counter -gt 9 ]; then
>    echo "libvirtd socket generation timed out" >> /var/log/virsh.log
>    fi
>    if pidof libvirtd &>/dev/null; then
>    LC_ALL=C /usr/bin/virsh -l /var/log/virsh.log start win10
>    if [ $? -gt 0 ]; then
>        echo "virsh was unsuccessful" >> /var/log/virsh.log
>        reboot
>    fi
>    else
>    echo "libvirtd is not started" >> /var/log/virsh.log
>    reboot
>    fi
>fi
>
>reboot is more convenient, since this is a vfio-igd passthrough vm.
>
>
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