[Xen-devel] [PATCH] VTD/Intremap: Disable Intremap on Chipset 5500/5520/X58 due to errata

[Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>]

http://www.intel.com/content/www/us/en/chipsets/5520-and-5500-chipset-ioh-specification-update.html

Stepping B-3 has two errata (#47 and #53) related to Interrupt
remapping, to which the workaround is for the BIOS to completely disable
interrupt remapping.  These errata are fixed in stepping C-2.

Unfortunately this chipset is very common and many BIOSes are not
disabling remapping.  We can detect this in Xen and prevent turning on
remapping in the first place.  However, this will turn VT-d off on many
systems by default.

Users who still wish to use VT-d can use iommu=force if they are happy
exposing the associated security risk.

Signed-off-by: Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

diff -r 35a0556a7f76 -r ee475f0e6aeb xen/drivers/passthrough/vtd/quirks.c
--- a/xen/drivers/passthrough/vtd/quirks.c
+++ b/xen/drivers/passthrough/vtd/quirks.c
@@ -244,6 +244,29 @@ void vtd_ops_postamble_quirk(struct iomm
     }
 }
 
+/* 5500/5520/X58 Chipset Interrupt remapping errata, for stepping B-3.
+ * Fixed in stepping C-2. */
+void __init tylersburg_intremap_quirk(void)
+{
+    uint32_t bus, device;
+    uint8_t rev;
+
+    for ( bus = 0; bus < 0x100; bus++ )
+    {
+        /* Match on System Management Registers on Device 20 Function 0 */
+        device = pci_conf_read32(0, bus, 20, 0, PCI_VENDOR_ID);
+        rev = pci_conf_read8(0, bus, 20, 0, PCI_REVISION_ID);
+
+        if ( rev == 0x13 && device == 0x342e8086 )
+        {
+            dprintk(XENLOG_INFO VTDPREFIX,
+                    "Disabling Interrupt Remapping due to Intel 5500/5520/X58 
Chipset errata #47, #53\n");
+            iommu_intremap = 0;
+            break;
+        }
+    }
+}
+
 /* initialize platform identification flags */
 void __init platform_quirks_init(void)
 {
@@ -264,6 +287,9 @@ void __init platform_quirks_init(void)
 
     /* ioremap IGD MMIO+0x2000 page */
     map_igd_reg();
+
+    /* Tylersburg interrupt remap quirk */
+    tylersburg_intremap_quirk();
 }
 
 /*

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