linux-kernel - Re: [PATCH 0/16] DMA-API debugging facility v2

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Message-ID: <20090206022759.GF27684@sequoia.sous-sol.org>
Date:	Thu, 5 Feb 2009 18:27:59 -0800
From:	Chris Wright <chrisw@...s-sol.org>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	Joerg Roedel <joerg.roedel@....com>, fujita.tomonori@....ntt.co.jp,
	netdev@...r.kernel.org, iommu@...ts.linux-foundation.org,
	mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/16] DMA-API debugging facility v2

* David Woodhouse (dwmw2@...radead.org) wrote:
> This adds a function to dump the DMA mappings that the debugging code is
> aware of -- either for a single device, or for _all_ devices.
> 
> This can be useful for debugging -- sticking a call to it in the DMA
> page fault handler, for example, to see if the faulting address _should_
> be mapped or not, and hence work out whether it's IOMMU bugs we're
> seeing, or driver bugs.

BTW, here's how I hooked it up:

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index c933980..df593d1 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -1072,6 +1072,34 @@ void dmar_msi_read(int irq, struct msi_msg *msg)
 	spin_unlock_irqrestore(&iommu->register_lock, flag);
 }
 
+static struct pci_dev *domain_find_pdev(u8 bus, u8 devfn)
+{
+	unsigned long flags;
+	struct pci_dev *pdev = NULL;
+	struct device_domain_info *info;
+
+	spin_lock_irqsave(&device_domain_lock, flags);
+	list_for_each_entry(info, &device_domain_list, global) {
+		if (info->bus == bus && info->devfn == devfn) {
+			pdev = info->dev;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&device_domain_lock, flags);
+	return pdev;
+}
+
+static void dump_mappings(u16 source_id)
+{
+	struct pci_dev *pdev;
+	u8 bus = source_id >> 8;
+	u8 devfn = source_id & 0xff;
+
+	pdev = domain_find_pdev(bus, devfn);
+	if (pdev)
+		debug_dma_dump_mappings(&pdev->dev);
+}
+
 static int iommu_page_fault_do_one(struct intel_iommu *iommu, int type,
 		u8 fault_reason, u16 source_id, unsigned long long addr)
 {
@@ -1086,6 +1114,8 @@ static int iommu_page_fault_do_one(struct intel_iommu *iommu, int type,
 		(type ? "DMA Read" : "DMA Write"),
 		(source_id >> 8), PCI_SLOT(source_id & 0xFF),
 		PCI_FUNC(source_id & 0xFF), addr, fault_reason, reason);
+
+	dump_mappings(source_id);
 	return 0;
 }
 
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