From: Wei Xu <xuwei5@hisilicon.com>
To: Will Deacon <will.deacon@arm.com>, James Morse <james.morse@arm.com>
Cc: <catalin.marinas@arm.com>, <suzuki.poulose@arm.com>,
<dave.martin@arm.com>, <mark.rutland@arm.com>,
<marc.zyngier@arm.com>, <linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, Linuxarm <linuxarm@huawei.com>,
Hanjun Guo <guohanjun@huawei.com>, <xiexiuqi@huawei.com>,
huangdaode <huangdaode@hisilicon.com>,
"Chenxin (Charles)" <charles.chenxin@huawei.com>,
"Xiongfanggou (James)" <james.xiong@huawei.com>,
"Liguozhu (Kenneth)" <liguozhu@hisilicon.com>,
Zhangyi ac <zhangyi.ac@huawei.com>, <jonathan.cameron@huawei.com>,
"Shameerali Kolothum Thodi"
<shameerali.kolothum.thodi@huawei.com>,
John Garry <john.garry@huawei.com>,
Salil Mehta <salil.mehta@huawei.com>,
Shiju Jose <shiju.jose@huawei.com>,
"Zhuangyuzeng (Yisen)" <yisen.zhuang@huawei.com>,
"Wangzhou (B)" <wangzhou1@hisilicon.com>,
"kongxinwei (A)" <kong.kongxinwei@hisilicon.com>,
"Liyuan (Larry, Turing Solution)" <Larry.T@huawei.com>,
<libeijian@hisilicon.com>
Subject: Re: KVM guest sometimes failed to boot because of kernel stack overflow if KPTI is enabled on a hisilicon ARM64 platform.
Date: Thu, 21 Jun 2018 11:14:28 +0100 [thread overview]
Message-ID: <5B2B7A84.8090309@hisilicon.com> (raw)
In-Reply-To: <20180621091850.GA22505@arm.com>
Hi Will,
On 2018/6/21 10:18, Will Deacon wrote:
> On Thu, Jun 21, 2018 at 09:38:53AM +0100, James Morse wrote:
>> On 20/06/18 17:25, Wei Xu wrote:
>>> [ 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.
>
> Hmm, one thing that occurs to me is that the kpti_install_ng_mappings()
> code leaves the nG bit set in table entries, which is actually IGNORED in
> the architecture.
>
> Wei -- does the diff below help at all? Make sure you disable CONFIG_KASAN,
> otherwise your kernel will take an age to boot.
Yes, amazing! This patch resolved the issue.
I have tested 50 times and can not reproduce the issue any more.
Could you please tell more why this patch works?
Thanks!
Best Regards,
Wei
>
> Will
>
> --->8
>
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index 5f9a73a4452c..70d9e98467ca 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -272,8 +272,8 @@ ENTRY(idmap_kpti_install_ng_mappings)
> add end_pgdp, cur_pgdp, #(PTRS_PER_PGD * 8)
> do_pgd: __idmap_kpti_get_pgtable_ent pgd
> tbnz pgd, #1, walk_puds
> -next_pgd:
> __idmap_kpti_put_pgtable_ent_ng pgd
> +next_pgd:
> skip_pgd:
> add cur_pgdp, cur_pgdp, #8
> cmp cur_pgdp, end_pgdp
> @@ -302,8 +302,8 @@ walk_puds:
> add end_pudp, cur_pudp, #(PTRS_PER_PUD * 8)
> do_pud: __idmap_kpti_get_pgtable_ent pud
> tbnz pud, #1, walk_pmds
> -next_pud:
> __idmap_kpti_put_pgtable_ent_ng pud
> +next_pud:
> skip_pud:
> add cur_pudp, cur_pudp, 8
> cmp cur_pudp, end_pudp
> @@ -323,8 +323,8 @@ walk_pmds:
> add end_pmdp, cur_pmdp, #(PTRS_PER_PMD * 8)
> do_pmd: __idmap_kpti_get_pgtable_ent pmd
> tbnz pmd, #1, walk_ptes
> -next_pmd:
> __idmap_kpti_put_pgtable_ent_ng pmd
> +next_pmd:
> skip_pmd:
> add cur_pmdp, cur_pmdp, #8
> cmp cur_pmdp, end_pmdp
>
> .
>
next prev parent reply other threads:[~2018-06-21 10:15 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-20 14:18 KVM guest sometimes failed to boot because of kernel stack overflow if KPTI is enabled on a hisilicon ARM64 platform Wei Xu
2018-06-20 14:42 ` Will Deacon
2018-06-20 15:52 ` Wei Xu
2018-06-20 15:54 ` James Morse
2018-06-20 16:25 ` Wei Xu
2018-06-20 16:28 ` Will Deacon
2018-06-20 16:33 ` Wei Xu
2018-06-21 8:38 ` James Morse
2018-06-21 9:00 ` Marc Zyngier
2018-06-21 9:18 ` Will Deacon
2018-06-21 10:14 ` Wei Xu [this message]
2018-06-21 10:54 ` Will Deacon
2018-06-22 8:33 ` Wei Xu
2018-06-22 9:23 ` Will Deacon
2018-06-22 10:45 ` Wei Xu
2018-06-22 11:16 ` Will Deacon
2018-06-22 13:18 ` Wei Xu
2018-06-22 13:31 ` Will Deacon
2018-06-22 13:46 ` Wei Xu
2018-06-22 14:43 ` Will Deacon
2018-06-22 15:26 ` Wei Xu
2018-06-22 14:28 ` Mark Rutland
2018-06-22 15:28 ` Wei Xu
2018-06-22 15:41 ` Will Deacon
2018-06-22 16:02 ` Wei Xu
2018-06-21 9:20 ` Wei Xu
2018-06-26 17:16 ` Wei Xu
2018-06-26 17:47 ` Will Deacon
2018-06-27 8:39 ` James Morse
2018-06-27 13:26 ` Wei Xu
2018-06-28 8:45 ` James Morse
2018-06-28 10:20 ` Wei Xu
2018-06-27 13:22 ` Wei Xu
2018-06-27 13:28 ` Will Deacon
2018-06-27 13:32 ` Wei Xu
2018-06-28 14:50 ` Wei Xu
2018-06-28 15:34 ` Mark Rutland
[not found] ` <etPan.5b3507f7.914aa16.1d6b@localhost>
2018-06-28 16:24 ` 答复: " Mark Rutland
2018-06-29 9:59 ` Mark Rutland
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