Message-ID: <b0d9f4ea-ed97-3bd4-7ddd-cc87043c8576@windriver.com>
Date:   Thu, 28 Dec 2017 10:05:26 +0800
From:   Cao Zou <cao.zou@...driver.com>
To:     Marc Zyngier <marc.zyngier@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:     <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

Hi lorenzo:

   What do you think?

Regards,

czou


On 12/22/2017 05:35 PM, Marc Zyngier wrote:
> On 22/12/17 07:38, Cao Zou wrote:
>>
>> On 12/22/2017 11:04 AM, Cao Zou wrote:
>>>
>>> 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
>>>
>> Hi Marc:
>>     I have a better way to fix it, just use dynamic allocate the irq_desc
>> in MSI irq setup,
>> remove the irq_desc allocate in dw_pcie_host_init, how do you think
>>
>> patch as follow:
>> diff --git a/drivers/pci/dwc/pcie-designware-host.c
>> b/drivers/pci/dwc/pcie-designware-host.c
>> index 5006d55..0426120 100644
>> --- a/drivers/pci/dwc/pcie-designware-host.c
>> +++ b/drivers/pci/dwc/pcie-designware-host.c
>> @@ -168,8 +168,12 @@ static int assign_irq(int no_irqs, struct msi_desc
>> *desc, int *pos)
>>                   goto no_valid_irq;
>>
>>           irq = irq_find_mapping(pp->irq_domain, pos0);
>> -       if (!irq)
>> -               goto no_valid_irq;
>> +
>> +       if (!irq) {
>> +               irq = irq_create_mapping(pp->irq_domain, pos0);
>> +               if (!irq)
>> +                       goto no_valid_irq;
>> +       }
>>
>>           /*
>>            * irq_create_mapping (called from dw_pcie_host_init) pre-allocates
>> @@ -408,9 +412,6 @@ int dw_pcie_host_init(struct pcie_port *pp)
>>                                   ret = -ENXIO;
>>                                   goto error;
>>                           }
>> -
>> -                       for (i = 0; i < MAX_MSI_IRQS; i++)
>> - irq_create_mapping(pp->irq_domain, i);
>>                   } else {
>>                           ret = pp->ops->msi_host_init(pp,
>> &dw_pcie_msi_chip);
>>                           if (ret < 0)
>>
> That's an option for *this* driver, but I'd rather you help Joao getting
> rid of this code altogether. It also ignores all the other drivers which
> suffer from the same defect.
>
> Joao, can you please point Cao to your existing patches?
>
> Thanks,
>
> 	M.

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