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

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Date:   Fri, 23 Jun 2017 13:19:23 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Alex Williamson <alex.williamson@...hat.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>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [RFC 7/9] iommu/dmar: notify unrecoverable faults

On Thu, 22 Jun 2017 16:54:16 -0600
Alex Williamson <alex.williamson@...hat.com> wrote:

> 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.
> 
same as before. pci_get_bus_and_slot() does not do ref counting.
> > +
> > +	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?
> 
good catch. I will drop the return code.
> > +	}
> > +
> >  	return 0;
> >  }
> >    
> 

[Jacob Pan]