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

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Message-ID: <d0b5fa66-e16d-8686-79e2-4d7177cd4806@gmail.com>
Date:   Wed, 29 Aug 2018 11:59:33 -0500
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, Narendra_K@...l.com,
        Stuart_Hayes@...l.com, lukas@...ner.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI/MSI: Don't touch MSI bits when the PCI device is
 disconnected

Should I resubmit this rebased on 4.19-rc*, or just leave this patch as is?

Alex

On 07/30/2018 04:21 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. pci_msi_(un)mask_irq 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 machines with buggy firmware.
> Not triggering the IO in the first place eliminates the problem.
> 
> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...il.com>
> ---
> 
> There's another patch by Lukas Wunner that is needed (not yet published)
> in order to fully block IO on SURPRISE!!! removal. The existing code only
> sets the PCI_DEV_DISCONNECTED bit in an unreasonably narrow set of
> circumstances. Lukas' patch fixes that.
> 
> However, this change is otherwise fully independent, and enjoy!
> 
>   drivers/pci/msi.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 4d88afdfc843..5f47b5cb0401 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 */
>