Messages in this thread | | | Subject | Re: KVM guest sometimes failed to boot because of kernel stack overflow if KPTI is enabled on a hisilicon ARM64 platform. | From | James Morse <> | Date | Thu, 21 Jun 2018 09:38:53 +0100 |
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Hi Will, Wei,
On 20/06/18 17:25, Wei Xu wrote: > On 2018/6/20 23:54, James Morse wrote: > I have disabled CONFIG_ARM64_RAS_EXTN and reverted that commit. > But I still got the stack overflow issue sometimes. > Do you have more hint?
> The log is as below: > [ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x480fd010] > [ 0.000000] Linux version 4.17.0-45865-g2b31fe7-dirty
Could you reproduce this with v4.17? This says there are ~45,000 extra patches, and un-committed changes. None of the hashes so far have been commits in mainline, so we have no idea what this tree is.
> (joyx@Turing-Arch-b) (gcc version 4.9.1 20140505 (prerelease) (crosstool-NG > linaro-1.13.1-4.9-2014.05 - Linaro GCC 4.9-2014.05)) #10 SMP PREEMPT Wed Jun 20 > 23:59:05 CST 2018
> [ 0.000000] CPU0: using LPI pending table @0x000000007d860000 > [ 0.000000] GIC: PPI11 is secure or misconfigured > [ 0.000000] arch_timer: WARNING: Invalid trigger for IRQ3, assuming level > low > [ 0.000000] arch_timer: WARNING: Please fix your firmware > [ 0.000000] arch_timer: cp15 timer(s) running at 100.00MHz (virt).
(No idea what these mean, but I doubt they are relevant)
> [ 0.042421] Insufficient stack space to handle exception! > [ 0.042423] ESR: 0x96000046 -- DABT (current EL) > [ 0.043730] FAR: 0xffff0000093a80e0 > [ 0.044714] Task stack: [0xffff0000093a8000..0xffff0000093ac000]
This was a level 2 translation fault on a write, to an address that is within the stack....
> [ 0.051113] IRQ stack: [0xffff000008000000..0xffff000008004000] > [ 0.057610] Overflow stack: [0xffff80003efce2f0..0xffff80003efcf2f0] > [ 0.064003] CPU: 0 PID: 12 Comm: migration/0 Not tainted > 4.17.0-45865-g2b31fe7-dirty #10 > [ 0.072201] Hardware name: linux,dummy-virt (DT)
> [ 0.076797] pstate: 604003c5 (nZCv DAIF +PAN -UAO) > [ 0.081727] pc : el1_sync+0x0/0xb0
... from the vectors.
> [ 0.085217] lr : kpti_install_ng_mappings+0x120/0x214
What I think is happening is: we come out of the kpti idmap with the stack unmapped. Shortly after we access the stack, which faults. el1_sync faults as well when it tries to push the registers to the stack, and we keep going until we overflow the stack.
I can't reproduce this with kvmtool or qemu in the model.
Thanks,
James
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