linux-kernel - Re: [PATCH v2] PCI/MSI: Don't touch MSI bits when the PCI device is disconnected

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Date:   Mon, 5 Nov 2018 18:32:02 -0600
From:   "Alex G." <mr.nuke.me@...il.com>
To:     linux-pci@...r.kernel.org, bhelgaas@...gle.com
Cc:     keith.busch@...el.com, alex_gagniuc@...lteam.com,
        austin_bolen@...l.com, shyam_iyer@...l.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI/MSI: Don't touch MSI bits when the PCI device is
 disconnected

ping

On 09/18/2018 05:15 PM, Alexandru Gagniuc wrote:
> When a PCI device is gone, we don't want to send IO to it if we can
> avoid it. We expose functionality via the irq_chip structure. As
> users of that structure may not know about the underlying PCI device,
> it's our responsibility to guard against removed devices.
> 
> .irq_write_msi_msg() is already guarded inside __pci_write_msi_msg().
> .irq_mask/unmask() are not. Guard them for completeness.
> 
> For example, surprise removal of a PCIe device triggers teardown. This
> touches the irq_chips ops some point to disable the interrupts. I/O
> generated here can crash the system on firmware-first machines.
> Not triggering the IO in the first place greatly reduces the
> possibility of the problem occurring.
> 
> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...il.com>
> ---
>   drivers/pci/msi.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index f2ef896464b3..f31058fd2260 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 (pci_dev_is_disconnected(msi_desc_to_pci_dev(desc)))
> +		return;
> +
>   	if (desc->msi_attrib.is_msix) {
>   		msix_mask_irq(desc, flag);
>   		readl(desc->mask_base);		/* Flush write to device */
>