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    SubjectRe: [PATCH] PCI: designware: add a check of msi_desc in irqchip
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    Date
    On 18/12/17 02:02, 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@windriver.com wrote:
    >>>> From: Zou Cao <cao.zou@windriver.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@windriver.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@arm.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@arm.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 exactly *one* warning. That's what the _ONCE suffix
    indicates. What makes you think that this doesn't solve your issue with
    kexec? If this doesn't work for you, please let me know why.

    In general, warnings are a good thing. They remind you that the software
    you're using is broken and needs fixing.

    Thanks,

    M.
    --
    Jazz is not dead. It just smells funny...

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