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SubjectRe: [PATCH v5 4/7] PCI: Add quirk to disable MSI-X support for Amazon's Annapurna Labs Root Port
s/Add quirk to disable/Disable/ in subject

On Thu, Sep 05, 2019 at 05:00:18PM +0300, Jonathan Chocron wrote:
> The Root Port (identified by [1c36:0031]) doesn't support MSI-X. On some
> platforms it is configured to not advertise the capability at all, while
> on others it (mistakenly) does. This causes a panic during
> initialization by the pcieport driver, since it tries to configure the
> MSI-X capability. Specifically, when trying to access the MSI-X table
> a "non-existing addr" exception occurs.

MSI-X configuration is all in memory space (not config space), so I
guess this device has a BAR (maybe more) and the MSI-X table access
would be to something in that BAR? Or is there junk in the capability
so we try to access something completely outside the BAR? [I wonder if
it'd be worth adding some validation to make sure the Table and PBA
areas are contained in the BAR?]

The reason I'm curious about all this is because on the PCI side this
is probably an Unsupported Request or similar error, and on *most*
platforms, this does not cause a panic. If it was a read, the read
usually gets ~0 data, and writes are dropped.

So my concern is that we'll avoid this panic by disabling MSI, but
we'll see other panics in other places.

> Example stacktrace snippet:

[Remove the timestamps since they're not really relevant and indent
the quote a couple spaces]

> [ 1.632363] SError Interrupt on CPU2, code 0xbf000000 -- SError
> [ 1.632364] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.2.0-rc1-Jonny-14847-ge76f1d4a1828-dirty #33
> [ 1.632365] Hardware name: Annapurna Labs Alpine V3 EVP (DT)
> [ 1.632365] pstate: 80000005 (Nzcv daif -PAN -UAO)
> [ 1.632366] pc : __pci_enable_msix_range+0x4e4/0x608
> [ 1.632367] lr : __pci_enable_msix_range+0x498/0x608
> [ 1.632367] sp : ffffff80117db700
> [ 1.632368] x29: ffffff80117db700 x28: 0000000000000001
> [ 1.632370] x27: 0000000000000001 x26: 0000000000000000
> [ 1.632372] x25: ffffffd3e9d8c0b0 x24: 0000000000000000
> [ 1.632373] x23: 0000000000000000 x22: 0000000000000000
> [ 1.632375] x21: 0000000000000001 x20: 0000000000000000
> [ 1.632376] x19: ffffffd3e9d8c000 x18: ffffffffffffffff
> [ 1.632378] x17: 0000000000000000 x16: 0000000000000000
> [ 1.632379] x15: ffffff80116496c8 x14: ffffffd3e9844503
> [ 1.632380] x13: ffffffd3e9844502 x12: 0000000000000038
> [ 1.632382] x11: ffffffffffffff00 x10: 0000000000000040
> [ 1.632384] x9 : ffffff801165e270 x8 : ffffff801165e268
> [ 1.632385] x7 : 0000000000000002 x6 : 00000000000000b2
> [ 1.632387] x5 : ffffffd3e9d8c2c0 x4 : 0000000000000000
> [ 1.632388] x3 : 0000000000000000 x2 : 0000000000000000
> [ 1.632390] x1 : 0000000000000000 x0 : ffffffd3e9844680
> [ 1.632392] Kernel panic - not syncing: Asynchronous SError Interrupt
> [ 1.632393] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.2.0-rc1-Jonny-14847-ge76f1d4a1828-dirty #33
> [ 1.632394] Hardware name: Annapurna Labs Alpine V3 EVP (DT)
> [ 1.632394] Call trace:
> [ 1.632395] dump_backtrace+0x0/0x140
> [ 1.632395] show_stack+0x14/0x20
> [ 1.632396] dump_stack+0xa8/0xcc
> [ 1.632396] panic+0x140/0x334
> [ 1.632397] nmi_panic+0x6c/0x70
> [ 1.632398] arm64_serror_panic+0x74/0x88
> [ 1.632398] __pte_error+0x0/0x28
> [ 1.632399] el1_error+0x84/0xf8
> [ 1.632400] __pci_enable_msix_range+0x4e4/0x608
> [ 1.632400] pci_alloc_irq_vectors_affinity+0xdc/0x150
> [ 1.632401] pcie_port_device_register+0x2b8/0x4e0
> [ 1.632402] pcie_portdrv_probe+0x34/0xf0
>
> Notice that this quirk also disables MSI (which may work, but hasn't
> been tested nor has a current use case), since currently there is no
> standard way to disable only MSI-X.
>
> Signed-off-by: Jonathan Chocron <jonnyc@amazon.com>
> Reviewed-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
> Reviewed-by: Andrew Murray <andrew.murray@arm.com>
> ---
> drivers/pci/quirks.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 8fe765592943..5a8ea5fdeae7 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -2977,6 +2977,24 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATTANSIC, 0x10a1,
> quirk_msi_intx_disable_qca_bug);
> DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATTANSIC, 0xe091,
> quirk_msi_intx_disable_qca_bug);
> +
> +/*
> + * Amazon's Annapurna Labs 1c36:0031 Root Ports don't support MSI-X, so it
> + * should be disabled on platforms where the device (mistakenly) advertises it.
> + *
> + * Notice that this quirk also disables MSI (which may work, but hasn't been
> + * tested), since currently there is no standard way to disable only MSI-X.
> + *
> + * The 0031 device id is reused for other non Root Port device types,
> + * therefore the quirk is registered for the PCI_CLASS_BRIDGE_PCI class.
> + */
> +static void quirk_al_msi_disable(struct pci_dev *dev)
> +{
> + dev->no_msi = 1;
> + pci_warn(dev, "Disabling MSI/MSI-X\n");
> +}
> +DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_AMAZON_ANNAPURNA_LABS, 0x0031,
> + PCI_CLASS_BRIDGE_PCI, 8, quirk_al_msi_disable);
> #endif /* CONFIG_PCI_MSI */
>
> /*
> --
> 2.17.1
>

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