Date:   Fri, 22 Dec 2017 15:38:08 +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 12/22/2017 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)

Regards,
czou

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