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

[Ard Biesheuvel <ardb@kernel.org>]

On Fri, 2 Dec 2022 at 03:48, chenxiang (M) <chenxiang66@hisilicon.com> wrote:
>
> Hi Ard,
>
>
> 在 2022/12/1 19:07, Ard Biesheuvel 写道:
> > On Thu, 1 Dec 2022 at 09:07, Ard Biesheuvel <ardb@kernel.org> wrote:
> >> 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.
> >>
> > ...but before I do that, could you please check whether the change
> > below fixes your issue as well?
> >
> > diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> > index 6ccc7ef600e7c1e1..c8c205b630da1951 100644
> > --- a/arch/arm64/kernel/kaslr.c
> > +++ b/arch/arm64/kernel/kaslr.c
> > @@ -20,7 +20,11 @@
> >   #include <asm/sections.h>
> >   #include <asm/setup.h>
> >
> > -u64 __ro_after_init module_alloc_base;
> > +/*
> > + * Set a reasonable default for module_alloc_base in case
> > + * we end up running with module randomization disabled.
> > + */
> > +u64 __ro_after_init module_alloc_base = (u64)_etext - MODULES_VSIZE;
> >   u16 __initdata memstart_offset_seed;
> >
> >   struct arm64_ftr_override kaslr_feature_override __initdata;
> > @@ -30,12 +34,6 @@ static int __init kaslr_init(void)
> >          u64 module_range;
> >          u32 seed;
> >
> > -       /*
> > -        * Set a reasonable default for module_alloc_base in case
> > -        * we end up running with module randomization disabled.
> > -        */
> > -       module_alloc_base = (u64)_etext - MODULES_VSIZE;
> > -
> >          if (kaslr_feature_override.val & kaslr_feature_override.mask & 0xf) {
> >                  pr_info("KASLR disabled on command line\n");
> >                  return 0;
> > .
>
> We have tested this change, the issue is still and it doesn't fix the issue.
>

Thanks for the report.