Re: regression: insmod module failed in VM with nvdimm on

[Ard Biesheuvel]

On Thu, 1 Dec 2022 at 08:15, chenxiang (M) <chenxiang66@hisilicon.com> wrote:
>
> Hi Ard,
>
>
> 在 2022/11/30 16:18, Ard Biesheuvel 写道:
> > On Wed, 30 Nov 2022 at 08:53, Marc Zyngier <maz@kernel.org> wrote:
> >> On Wed, 30 Nov 2022 02:52:35 +0000,
> >> "chenxiang (M)" <chenxiang66@hisilicon.com> wrote:
> >>> Hi,
> >>>
> >>> We boot the VM using following commands (with nvdimm on)  (qemu
> >>> version 6.1.50, kernel 6.0-r4):
> >> How relevant is the presence of the nvdimm? Do you observe the failure
> >> without this?
> >>
> >>> qemu-system-aarch64 -machine
> >>> virt,kernel_irqchip=on,gic-version=3,nvdimm=on  -kernel
> >>> /home/kernel/Image -initrd /home/mini-rootfs/rootfs.cpio.gz -bios
> >>> /root/QEMU_EFI.FD -cpu host -enable-kvm -net none -nographic -m
> >>> 2G,maxmem=64G,slots=3 -smp 4 -append 'rdinit=init console=ttyAMA0
> >>> ealycon=pl0ll,0x90000000 pcie_ports=native pciehp.pciehp_debug=1'
> >>> -object memory-backend-ram,id=ram1,size=10G -device
> >>> nvdimm,id=dimm1,memdev=ram1  -device ioh3420,id=root_port1,chassis=1
> >>> -device vfio-pci,host=7d:01.0,id=net0,bus=root_port1
> >>>
> >>> Then in VM we insmod a module, vmalloc error occurs as follows (kernel
> >>> 5.19-rc4 is normal, and the issue is still on kernel 6.1-rc4):
> >>>
> >>> estuary:/$ insmod /lib/modules/$(uname -r)/hnae3.ko
> >>> [    8.186563] vmap allocation for size 20480 failed: use
> >>> vmalloc=<size> to increase size
> >> Have you tried increasing the vmalloc size to check that this is
> >> indeed the problem?
> >>
> >> [...]
> >>
> >>> We git bisect the code, and find the patch c5a89f75d2a ("arm64: kaslr:
> >>> defer initialization to initcall where permitted").
> >> I guess you mean commit fc5a89f75d2a instead, right?
> >>
> >>> Do you have any idea about the issue?
> >> I sort of suspect that the nvdimm gets vmap-ed and consumes a large
> >> portion of the vmalloc space, but you give very little information
> >> that could help here...
> >>
> > Ouch. I suspect what's going on here: that patch defers the
> > randomization of the module region, so that we can decouple it from
> > the very early init code.
> >
> > Obviously, it is happening too late now, and the randomized module
> > region is overlapping with a vmalloc region that is in use by the time
> > the randomization occurs.
> >
> > Does the below fix the issue?
>
> The issue still occurs, but it seems decrease the probability, before it
> occured almost every time, after the change, i tried 2-3 times, and it
> occurs.
> But i change back "subsys_initcall" to "core_initcall", and i test more
> than 20 times, and it is still ok.
>

Thank you for confirming. I will send out a patch today.

> >
> > diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> > index 37a9deed2aec..71fb18b2f304 100644
> > --- a/arch/arm64/kernel/kaslr.c
> > +++ b/arch/arm64/kernel/kaslr.c
> > @@ -90,4 +90,4 @@ static int __init kaslr_init(void)
> >
> >          return 0;
> >   }
> > -subsys_initcall(kaslr_init)
> > +arch_initcall(kaslr_init)
> > .
> >
>