From: Will Deacon <will.deacon@arm.com>
To: James Morse <james.morse@arm.com>
Cc: Wei Xu <xuwei5@hisilicon.com>,
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 10:18:51 +0100 [thread overview]
Message-ID: <20180621091850.GA22505@arm.com> (raw)
In-Reply-To: <e701eaa8-dcb9-777c-2211-67ee27b43acb@arm.com>
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.
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 9:18 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 [this message]
2018-06-21 10:14 ` Wei Xu
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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