linux-kernel - Re: [RFC 7/9] iommu/dmar: notify unrecoverable faults

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Date:   Thu, 22 Jun 2017 16:54:16 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        Lan Tianyu <tianyu.lan@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Jean Delvare <khali@...ux-fr.org>
Subject: Re: [RFC 7/9] iommu/dmar: notify unrecoverable faults

On Wed, 14 Jun 2017 15:23:01 -0700
Jacob Pan <jacob.jun.pan@...ux.intel.com> wrote:

> Currently, when device DMA faults are detected by IOMMU the fault
> reasons are printed but the offending device is not notified.
> This patch allows device drivers to be optionally notified for fault
> conditions when device specific handling is needed for more subtle
> processing, e.g. request with PASID transactions.
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Signed-off-by: Ashok Raj <ashok.raj@...el.com>
> ---
>  drivers/iommu/dmar.c | 37 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
> index cbf7763..2c0b80d464 100644
> --- a/drivers/iommu/dmar.c
> +++ b/drivers/iommu/dmar.c
> @@ -1587,11 +1587,43 @@ void dmar_msi_read(int irq, struct msi_msg *msg)
>  	raw_spin_unlock_irqrestore(&iommu->register_lock, flag);
>  }
>  
> +static int dmar_unrecov_fault_notify(u8 fault_reason, u16 source_id,
> +			unsigned long long addr)
> +{
> +	int ret;
> +	struct pci_dev *pdev;
> +	struct iommu_fault_event *event;
> +
> +	pdev = pci_get_bus_and_slot(source_id >> 8, source_id & 0xFF);
> +	if (!pdev)
> +		return -ENODEV;
> +	pr_debug("Notify PCI device fault [%02x:%02x.%d]\n",
> +		source_id >> 8, PCI_SLOT(source_id & 0xff),
> +		PCI_FUNC(source_id & 0xff));
> +	event = kzalloc(sizeof(*event) + sizeof(fault_reason), GFP_KERNEL);
> +	if (!event)
> +		return -ENOMEM;

Leaks pdev reference.

> +
> +	pci_dev_get(pdev);
> +	event->dev = &pdev->dev;
> +	event->buf[0] = fault_reason;
> +	event->addr = addr;
> +	event->length = sizeof(fault_reason);
> +	event->flags = IOMMU_FAULT_UNRECOV;
> +	ret = iommu_fault_notifier_call_chain(event);
> +
> +	pci_dev_put(pdev);
> +	kfree(event);
> +
> +	return ret;
> +}
> +
>  static int dmar_fault_do_one(struct intel_iommu *iommu, int type,
>  		u8 fault_reason, u16 source_id, unsigned long long addr)
>  {
>  	const char *reason;
>  	int fault_type;
> +	int ret = 0;
>  
>  	reason = dmar_get_fault_reason(fault_reason, &fault_type);
>  
> @@ -1600,11 +1632,14 @@ static int dmar_fault_do_one(struct intel_iommu *iommu, int type,
>  			source_id >> 8, PCI_SLOT(source_id & 0xFF),
>  			PCI_FUNC(source_id & 0xFF), addr >> 48,
>  			fault_reason, reason);
> -	else
> +	else {
>  		pr_err("[%s] Request device [%02x:%02x.%d] fault addr %llx [fault reason %02d] %s\n",
>  		       type ? "DMA Read" : "DMA Write",
>  		       source_id >> 8, PCI_SLOT(source_id & 0xFF),
>  		       PCI_FUNC(source_id & 0xFF), addr, fault_reason, reason);
> +		ret = dmar_unrecov_fault_notify(fault_reason, source_id, addr);

For what purpose are we recording this return code?

> +	}
> +
>  	return 0;
>  }
>