Message-ID: <9f0e2186-08e3-3ef1-87d5-83589f960b4f@windriver.com>
Date:   Fri, 22 Dec 2017 11:04:16 +0800
From:   Cao Zou <cao.zou@...driver.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:     Marc Zyngier <marc.zyngier@....com>, <jingoohan1@...il.com>,
        <Joao.Pinto@...opsys.com>, <bhelgaas@...gle.com>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI: designware: add a check of msi_desc in irqchip



On 12/20/2017 12:20 AM, Lorenzo Pieralisi wrote:
> On Mon, Dec 18, 2017 at 10:02:20AM +0800, Cao Zou wrote:
>>
>> On 12/16/2017 01:20 AM, Marc Zyngier wrote:
>>> On 15/12/17 16:17, Lorenzo Pieralisi wrote:
>>>> [+Marc]
>>>>
>>>> On Thu, Dec 14, 2017 at 10:21:23AM +0800, cao.zou@...driver.com wrote:
>>>>> From: Zou Cao <cao.zou@...driver.com>
>>>>>
>>>>> When PCIE host setup, 32 MSI irq descriptions are created, but its
>>>>> msi_desc is NULL, msi_desc is bound in MSI irq requested by PCI device,
>>>>> normally just part of MSI are used, for others not used MSI irqs, its
>>>>> msi_desc is NULL, it is dangerous for MSI irq mask when MSI irq mask use
>>>>> the msi_desc to mask irq without checking, normally not used MSI irqs are
>>>>> never masked, it looks fine, but in some specified case, such as kdump,
>>>>> machine_kexec_mask_interrupts will force to mask these not used MSI irqs,
>>>>> than a crash will happen with NULL msi_desc. it is necessary to add check
>>>>> of msi_desc in irqchip, if we still bind the msi_desc only in irqs request
>>>>> and mask MSI irq by msi_desc.
>>>>>
>>>>> Add dwc_pci_msi_mask/unmask_irq, so we can get a chance to check the
>>>>> msi_desc.
>>>>>
>>>>> here is reproduced crash log in IMX7-SABER board with Intel 1030 PCI,
>>>>> when running kdump by "echo c > /proc/sysrq-trigger":
>>>>>
>>>>> sysrq: SysRq : Trigger a crash
>>>>> Unable to handle kernel NULL pointer dereference at virtual address 00000000
>>>>> pgd = 98ee1839
>>>>> [00000000] *pgd=00000000
>>>>> Internal error: Oops: 805 [#1] SMP ARM
>>>>> Modules linked in:
>>>>> CPU: 0 PID: 1370 Comm: sh Not tainted 4.15.0-rc3-00033-ga638349 #1
>>>>> Hardware name: Freescale i.MX7 Dual (Device Tree)
>>>>> PC is at sysrq_handle_crash+0x50/0x98
>>>>> LR is at sysrq_handle_crash+0x50/0x98
>>>>> <snip>
>>>>> Backtrace:
>>>>> [<c047a15c>] (msi_set_mask_bit) from [<c047a1f0>] (pci_msi_mask_irq+0x14/0x18)
>>>>> [<c047a1dc>] (pci_msi_mask_irq) from [<c011142c>] (machine_crash_shutdown+0xd8/0x190)
>>>>> [<c0111354>] (machine_crash_shutdown) from [<c01b2924>] (__crash_kexec+0x5c/0xa0)
>>>>> [<c01b28c8>] (__crash_kexec) from [<c01b29dc>] (crash_kexec+0x74/0x80)
>>>>> [<c01b2968>] (crash_kexec) from [<c010cfa4>] (die+0x220/0x358)
>>>>> [<c010cd84>] (die) from [<c01169f0>] (__do_kernel_fault.part.0+0x5c/0x7c)
>>>>> [<c0116994>] (__do_kernel_fault.part.0) from [<c0116784>] (do_page_fault+0x2cc/0x37c)
>>>>> [<c01164b8>] (do_page_fault) from [<c0116970>] (do_translation_fault+0xb0/0xbc)
>>>>> [<c01168c0>] (do_translation_fault) from [<c010138c>] (do_DataAbort+0x3c/0xbc)
>>>>> [<c0101350>] (do_DataAbort) from [<c010d944>] (__dabt_svc+0x64/0xa0)
>>>>> Exception stack(0xec08bdf8 to 0xec08be40)
>>>>> bde0:                                                       00000000 ec08be10
>>>>> be00: 00000000 00000000 00000000 00000001 00000063 00000000 00000007 ec08a000
>>>>> be20: 00000000 ec08be5c ec08be48 ec08be48 c04c46b8 c04c46b8 60060013 ffffffff
>>>>> [<c04c4668>] (sysrq_handle_crash) from [<c04c4900>] (__handle_sysrq+0xe0/0x254)
>>>>> [<c04c4820>] (__handle_sysrq) from [<c04c4aec>] (write_sysrq_trigger+0x78/0x90)
>>>>> [<c04c4a74>] (write_sysrq_trigger) from [<c029148c>] (proc_reg_write+0x68/0x90)
>>>>> [<c0291424>] (proc_reg_write) from [<c0229ef8>] (__vfs_write+0x34/0x12c)
>>>>> [<c0229ec4>] (__vfs_write) from [<c022a16c>] (vfs_write+0xa8/0x16c)
>>>>> [<c022a0c4>] (vfs_write) from [<c022a340>] (SyS_write+0x44/0x90)
>>>>> [<c022a2fc>] (SyS_write) from [<c0108220>] (ret_fast_syscall+0x0/0x28)
>>>>>
>>>>> Signed-off-by: Zou Cao <cao.zou@...driver.com>
>>>>> ---
>>>>>   drivers/pci/dwc/pcie-designware-host.c | 24 ++++++++++++++++++++----
>>>>>   1 file changed, 20 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
>>>>> index 81e2157..485c4df 100644
>>>>> --- a/drivers/pci/dwc/pcie-designware-host.c
>>>>> +++ b/drivers/pci/dwc/pcie-designware-host.c
>>>>> @@ -45,12 +45,28 @@ static int dw_pcie_wr_own_conf(struct pcie_port *pp, int where, int size,
>>>>>   	return dw_pcie_write(pci->dbi_base + where, size, val);
>>>>>   }
>>>>> +static void dwc_pci_msi_mask_irq(struct irq_data *data)
>>>>> +{
>>>>> +	struct msi_desc *desc = irq_data_get_msi_desc(data);
>>>>> +
>>>>> +	if (desc)
>>>>> +		pci_msi_mask_irq(data);
>>>>> +}
>>>>> +
>>>>> +static void dwc_pci_msi_unmask_irq(struct irq_data *data)
>>>>> +{
>>>>> +	struct msi_desc *desc = irq_data_get_msi_desc(data);
>>>>> +
>>>>> +	if (desc)
>>>>> +		pci_msi_unmask_irq(data);
>>>>> +}
>>>>> +
>>>>>   static struct irq_chip dw_msi_irq_chip = {
>>>>>   	.name = "PCI-MSI",
>>>>> -	.irq_enable = pci_msi_unmask_irq,
>>>>> -	.irq_disable = pci_msi_mask_irq,
>>>>> -	.irq_mask = pci_msi_mask_irq,
>>>>> -	.irq_unmask = pci_msi_unmask_irq,
>>>>> +	.irq_enable = dwc_pci_msi_unmask_irq,
>>>>> +	.irq_disable = dwc_pci_msi_mask_irq,
>>>>> +	.irq_mask = dwc_pci_msi_mask_irq,
>>>>> +	.irq_unmask = dwc_pci_msi_unmask_irq,
>>>>>   };
>>>> You have to CC me next time please.
>>>>
>>>> CC'ed Marc since he knows this code ways better than me and will
>>>> help us find the right way of fixing it.
>>>>
>>>> I do not think that's a DWC-only problem - I see no reason why this
>>>> would not affect other host bridges still relying on
>>>> struct msi_controller (that we have to remove from the kernel).
>>>>
>>>> I do not think that this code is an actual fix but a plaster to
>>>> paper over the issue - I will have a look into this as soon as
>>>> possible to come up with an actual fix.
>>> Yeah, this looks mad. The problem is that this seems to allocate
>>> interrupts upfront, without being bound to an MSI. What could possibly
>>> go wrong? And that's definitely not the only one (pci-tegra.c is one
>>> fine example too).
>>>
>>> Until we take msi_controller and co to the backyard, how about the
>>> following:
>>>
>>> >From b4aa5d20ee7b716795ac875e180f564fe0f52de6 Mon Sep 17 00:00:00 2001
>>> From: Marc Zyngier <marc.zyngier@....com>
>>> Date: Fri, 15 Dec 2017 17:10:14 +0000
>>> Subject: [PATCH] PCI/MSI: Don't try to mask/unmask an MSI that doesn't have an
>>>   msi_desc
>>>
>>> There are a lot of MSI drivers out there that preallocate their
>>> interrupts but not the corresponding MSIs. That's a prettty
>>> naughty behaviour. On a kexec crash, we try to shut down all
>>> the interrupts by calling the disable/mask methods.
>>>
>>> On these drivers, pci_msi_mask_irq() is unconditionnaly called,
>>> leading to a crash. You wanted a crash kernel, right?
>>>
>>> So let's paper over the issue for the time being by detecting
>>> the NULL msi_desc in msi_set_mask_bit(). Eventually, these drivers
>>> will have to be fixed...
>>>
>>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>>> ---
>>>   drivers/pci/msi.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
>>> index e06607167858..a5042cc8f3fc 100644
>>> --- a/drivers/pci/msi.c
>>> +++ b/drivers/pci/msi.c
>>> @@ -227,6 +227,9 @@ static void msi_set_mask_bit(struct irq_data *data, u32 flag)
>>>   {
>>>   	struct msi_desc *desc = irq_data_get_msi_desc(data);
>>> +	if (WARN_ONCE(!desc, "NULL MSI descriptor!"))
>>> +		return;
>>> +
>>>   	if (desc->msi_attrib.is_msix) {
>>>   		msix_mask_irq(desc, flag);
>>>   		readl(desc->mask_base);		/* Flush write to device */
>> For "if (WARN_ONCE(!desc, "NULL MSI descriptor!")",  it is a good way,
>> just one problem. how to fix the kexec/kdump?  this WARN_ONCE can tell
>> the pci dirver to fix the MIS bound problem, but in kexec/kdump, it
>> will force to mask all MSI,  it means that there are a lot of WARNINGS
>> when running kexec/kdump.
> There will be one warning as Marc said. Mind testing Marc's patch
> and reporting the result on the mailing list please if you want
> the issue fixed ?
>
> Thanks,
> Lorenzo
>
Hi Lorenzo:
   Of course it can fix this issue, but  warning will be seen in every  
time when running kdump


root@...-imx7:~# echo c > /proc/sysrandom: crng init done

sys/           sysrq-trigger  sysvipc/
root@...-imx7:~# echo c > /proc/sysrq-trigger
sysrq: SysRq : Trigger a crash
Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = a9470000
[00000000] *pgd=a9474835, *pte=00000000, *ppte=00000000
Internal error: Oops: 817 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 369 Comm: sh Not tainted 4.12.14-yocto-standard+ #98
Hardware name: Freescale i.MX7 Dual (Device Tree)
task: a86e5400 task.stack: a9438000
PC is at sysrq_handle_crash+0x30/0x3c
LR is at sysrq_handle_crash+0x2c/0x3c
pc : [<8059576c>]    lr : [<80595768>]    psr: 600e0013
sp : a9439eb8  ip : a9439eb8  fp : a9439ecc
r10: 00000000  r9 : a9438000  r8 : 00000001
r7 : 00000000  r6 : 00000063  r5 : 00000007  r4 : 00000001
r3 : 00000000  r2 : a9439ea0  r1 : ab615434  r0 : 00000063
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 10c5387d  Table: a947006a  DAC: 00000051
Process sh (pid: 369, stack limit = 0xa9438210)
Stack: (0xa9439eb8 to 0xa943a000)
9ea0:                                                       8059573c 
8106f41c
9ec0: a9439eec a9439ed0 80595968 80595748 00000002 a8451444 a8451400 
00000000
9ee0: a9439f04 a9439ef0 80595a78 805958c4 a9439f78 a8451444 a9439f2c 
a9439f08
9f00: 802c570c 80595a1c 802c5698 00000000 00000002 001042a8 a9439f78 
001042a8
9f20: a9439f44 a9439f30 80268078 802c56a4 a9439f78 a901d6c0 a9439f74 
a9439f48
9f40: 80269598 8026805c 80286cac 80286c1c 00000000 00000000 a901d6c0 
a901d6c0
9f60: 00000002 001042a8 a9439fa4 a9439f78 8026982c 802694e4 00000000 
00000000
9f80: 00000002 001042a8 76f19da8 00000004 80107f68 00000000 00000000 
a9439fa8
9fa0: 80107d60 802697ec 00000002 001042a8 00000001 001042a8 00000002 
00000000
9fc0: 00000002 001042a8 76f19da8 00000004 00000002 00000002 00000000 
00000000
9fe0: 00000444 7e9d4980 76e466f0 76e9e41c 600e0010 00000001 3dbfa0e8 
a39746c6
[<8059576c>] (sysrq_handle_crash) from [<80595968>] 
(__handle_sysrq+0xb0/0x158)
[<80595968>] (__handle_sysrq) from [<80595a78>] 
(write_sysrq_trigger+0x68/0x78)
[<80595a78>] (write_sysrq_trigger) from [<802c570c>] 
(proc_reg_write+0x74/0xa4)
[<802c570c>] (proc_reg_write) from [<80268078>] (__vfs_write+0x28/0x48)
[<80268078>] (__vfs_write) from [<80269598>] (vfs_write+0xc0/0x164)
[<80269598>] (vfs_write) from [<8026982c>] (SyS_write+0x4c/0x8c)
[<8026982c>] (SyS_write) from [<80107d60>] (ret_fast_syscall+0x0/0x3c)
Code: e5834000 f57ff04e ebee0bee e3a03000 (e5c34000)
------------[ cut here ]------------
WARNING: CPU: 0 PID: 369 at 
/export/disk1T/linux-yocto-4.12/drivers/pci/msi.c:230 
msi_set_mask_bit+0x50/0xb0
NULL MSI descriptor!
Modules linked in:
CPU: 0 PID: 369 Comm: sh Not tainted 4.12.14-yocto-standard+ #98
Hardware name: Freescale i.MX7 Dual (Device Tree)
[<80111a50>] (unwind_backtrace) from [<8010c110>] (show_stack+0x20/0x24)
[<8010c110>] (show_stack) from [<804cb3dc>] (dump_stack+0x80/0xa0)
[<804cb3dc>] (dump_stack) from [<8012a2f4>] (__warn+0xe4/0x114)
[<8012a2f4>] (__warn) from [<8012a3f4>] (warn_slowpath_fmt+0x48/0x50)
[<8012a3f4>] (warn_slowpath_fmt) from [<8052f380>] 
(msi_set_mask_bit+0x50/0xb0)
[<8052f380>] (msi_set_mask_bit) from [<8052f41c>] 
(pci_msi_mask_irq+0x1c/0x20)
[<8052f41c>] (pci_msi_mask_irq) from [<80110224>] 
(machine_crash_shutdown+0x108/0x174)
[<80110224>] (machine_crash_shutdown) from [<801a7244>] 
(__crash_kexec+0x88/0xac)
[<801a7244>] (__crash_kexec) from [<801a72d0>] (crash_kexec+0x68/0x78)
[<801a72d0>] (crash_kexec) from [<8010c46c>] (die+0x358/0x47c)
[<8010c46c>] (die) from [<8011ccbc>] (__do_kernel_fault.part.0+0x64/0x1f4)
[<8011ccbc>] (__do_kernel_fault.part.0) from [<80ade250>] 
(do_page_fault+0x348/0x3d4)
[<80ade250>] (do_page_fault) from [<801011f8>] (do_DataAbort+0x44/0xc4)
[<801011f8>] (do_DataAbort) from [<80add5b8>] (__dabt_svc+0x58/0x80)
Exception stack(0xa9439e68 to 0xa9439eb0)
9e60:                   00000063 ab615434 a9439ea0 00000000 00000001 
00000007
9e80: 00000063 00000000 00000001 a9438000 00000000 a9439ecc a9439eb8 
a9439eb8
9ea0: 80595768 8059576c 600e0013 ffffffff
[<80add5b8>] (__dabt_svc) from [<8059576c>] (sysrq_handle_crash+0x30/0x3c)
[<8059576c>] (sysrq_handle_crash) from [<80595968>] 
(__handle_sysrq+0xb0/0x158)
[<80595968>] (__handle_sysrq) from [<80595a78>] 
(write_sysrq_trigger+0x68/0x78)
[<80595a78>] (write_sysrq_trigger) from [<802c570c>] 
(proc_reg_write+0x74/0xa4)
[<802c570c>] (proc_reg_write) from [<80268078>] (__vfs_write+0x28/0x48)
[<80268078>] (__vfs_write) from [<80269598>] (vfs_write+0xc0/0x164)
[<80269598>] (vfs_write) from [<8026982c>] (SyS_write+0x4c/0x8c)
[<8026982c>] (SyS_write) from [<80107d60>] (ret_fast_syscall+0x0/0x3c)
---[ end trace 7a853bb920d02801 ]---
Loading crashdump kernel...
Bye!
Booting Linux on physical CPU 0x0
Linux version 4.12.14-yocto-standard+ (czou@...-czou-u14) (gcc version 
4.7.3 20130226 (prerelease) (crosstool-NG 
linaro-1.13.1-4.7-2013.03-20130313 - Linaro GCC 2013.03) ) #98 SMP 
PREEMPT Fri Dec 22 10:59:43 CST7
CPU: ARMv7 Processor [410fc075] revision 5 (ARMv7), cr=10c5387d
CPU: div instructions available: patching division code
CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
OF: fdt: Machine model: Freescale i.MX7 SabreSD Board
OF: fdt: Ignoring memory range 0x80000000 - 0x88000000
Memory policy: Data cache writealloc
OF: reserved mem: failed to allocate memory for node 'linux,cma'
cma: Failed to reserve 320 MiB
percpu: Embedded 17 pages/cpu @8fc75000 s38016 r8192 d23424 u69632
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 64706
Kernel command line: console=ttymxc0,115200 root=/dev/nfs ip=dhcp 
nfsroot=128.224.162.234:/var/lib/tftp/nfs/rootfs_imx7wrl10,v3 maxcpus=1 
elfcorehdr=0x9cf00000 mem=261120K
PID hash table entries: 1024 (order: 0, 4096 bytes)
Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
Memory: 241716K/261120K available (10240K kernel code, 778K rwdata, 
2388K rodata, 1024K init, 364K bss, 19404K reserved, 0K cma-reserved, 0K 
highmem)
Virtual kernel memory layout:
     vector  : 0xffff0000 - 0xffff1000   (   4 kB)
     fixmap  : 0xffc00000 - 0xfff00000   (3072 kB)
     vmalloc : 0x90000000 - 0xff800000   (1784 MB)
     lowmem  : 0x80000000 - 0x8ff00000   ( 255 MB)
     pkmap   : 0x7fe00000 - 0x80000000   (   2 MB)

Regards,
czou

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