Message-ID: <20180109163811.GC16285@red-moon>
Date:   Tue, 9 Jan 2018 16:38:11 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Cao Zou <cao.zou@...driver.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 Thu, Dec 28, 2017 at 10:05:26AM +0800, Cao Zou wrote:
> Hi lorenzo:
> 
>   What do you think?

I told you what I think about this specific issue and I share
Marc's point of view.

FYI, Gustavo's patches to achieve the end goal:

https://patchwork.ozlabs.org/patch/854704/

> 
> 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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