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

[chenxiang (M)]

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.

> 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)
> .