linux-kernel - [PATCH v3] irq_remap: disable IRQ remapping if any IOAPIC lacks an IOMMU

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Date:	Wed,  8 Aug 2012 08:27:03 -0500
From:	Seth Forshee <seth.forshee@...onical.com>
To:	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	x86@...nel.org
Cc:	Joerg Roedel <joro@...tes.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Len Brown <lenb@...nel.org>,
	Joerg Roedel <joerg.roedel@....com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Yinghai Lu <yinghai@...nel.org>
Subject: [PATCH v3] irq_remap: disable IRQ remapping if any IOAPIC lacks an IOMMU

The ACPI tables in the Macbook Air 5,1 define a single IOAPIC with id 2,
but the only remapping unit described in the DMAR table matches id 0.
Interrupt remapping fails as a result, and the kernel panics with the
message "timer doesn't work through Interrupt-remapped IO-APIC."

To fix this, check each IOAPIC for a corresponding IOMMU. If an IOMMU is
not found, do not allow IRQ remapping to be enabled.

v2: Move check to parse_ioapics_under_ir(), raise log level to KERN_ERR,
    and add FW_BUG to the log message
v3: Skip check if IOMMU doesn't support interrupt remapping and remove
    existing check that the IOMMU count equals the IOAPIC count

Acked-by: Suresh Siddha <suresh.b.siddha@...el.com>
Signed-off-by: Seth Forshee <seth.forshee@...onical.com>
---
 drivers/iommu/intel_irq_remapping.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index e0b18f3..af8904d 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -736,6 +736,7 @@ int __init parse_ioapics_under_ir(void)
 {
 	struct dmar_drhd_unit *drhd;
 	int ir_supported = 0;
+	int ioapic_idx;
 
 	for_each_drhd_unit(drhd) {
 		struct intel_iommu *iommu = drhd->iommu;
@@ -748,13 +749,20 @@ int __init parse_ioapics_under_ir(void)
 		}
 	}
 
-	if (ir_supported && ir_ioapic_num != nr_ioapics) {
-		printk(KERN_WARNING
-		       "Not all IO-APIC's listed under remapping hardware\n");
-		return -1;
+	if (!ir_supported)
+		return 0;
+
+	for (ioapic_idx = 0; ioapic_idx < nr_ioapics; ioapic_idx++) {
+		int ioapic_id = mpc_ioapic_id(ioapic_idx);
+		if (!map_ioapic_to_ir(ioapic_id)) {
+			pr_err(FW_BUG "ioapic %d has no mapping iommu, "
+			       "interrupt remapping will be disabled\n",
+			       ioapic_id);
+			return -1;
+		}
 	}
 
-	return ir_supported;
+	return 1;
 }
 
 int __init ir_dev_scope_init(void)
-- 
1.7.9.5

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