[Xen-devel] [PATCH v2] AMD/IO-APIC: Use old IO-APIC ack method if AMD 813{1, 2} PCI-X tunnel is present

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

References at time of patch:

AMD 8132 PCI-X HyperTransport Tunnel
http://support.amd.com/us/ChipsetMotherboard_TechDocs/30801.pdf

AMD 8131 PCI-X HyperTransport Tunnel
http://support.amd.com/us/ChipsetMotherboard_TechDocs/26310_AMD-8131_HyperTransport_PCI-X_Tunnel_Revision_Guide_rev_3_18.pdf

The IO-APICs on the above two PCI-X HyperTransport Tunnels will issue illegal
HT packets if an interrupt gets masked while active.

This is sadly exactly what the "new" IO-APIC ack mode does.  The "old" ack
mode does however avoid this bad behaviour, and stabilises an affected system
belonging to a customer.

Original patch:
Signed-off-by: Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>

Forward ported and tweaked for upstream:
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

--
Changes since v1:
 * In the case that ioapic_ack_mode is specified on the command line, warn if
   instability will ensue.

diff -r 2d37d2d652a8 -r 115069a50a65 xen/arch/x86/io_apic.c
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -2016,8 +2016,76 @@ static void __init ioapic_pm_state_alloc
     BUG_ON(ioapic_pm_state == NULL);
 }
 
+/* AMD 8131 and 8132 PCI-X HyperTransport Tunnel IO-APICs will issue illegal
+ * HyperTransport packets if an interrupt is masked while active.  This leads
+ * to system instability and crashes with no obvious cause.
+ *
+ * This is sadly the exact behaviour of the "new" IO-APIC ack mode, but using
+ * "old" mode works around the issue.
+ */
+void __init amd813x_errata_quirks(void)
+{
+    unsigned i, found = 0;
+    uint32_t bus, dev, vendor_id;
+
+    if ( boot_cpu_data.x86_vendor != X86_VENDOR_AMD )
+        return;
+
+    /* Check for the affected IO-APIC version (0x11) to save scanning the PCI
+     * bus on most systems. */
+    for ( i = 0; i < nr_ioapics; ++i )
+    {
+        if ( mp_ioapics[i].mpc_apicver == 0x11 )
+        {
+            found = 1;
+            break;
+        }
+    }
+
+    if ( !found )
+        return;
+
+    for ( bus = 0; bus < 256; ++bus )
+    {
+        for ( dev = 0; dev < 32; ++dev )
+        {
+            /* IO-APIC is always Function 1.  Check for Multifunction. */
+            if ( !( pci_conf_read8(0, bus, dev, 0, PCI_HEADER_TYPE ) & 0x80 ) )
+                continue;
+
+            vendor_id = pci_conf_read32(0, bus, dev, 1, PCI_VENDOR_ID);
+
+            /* 0x7451 is AMD-8131 PCI-X IO-APIC */
+            if ( vendor_id == 0x74511022 )
+                printk(XENLOG_WARNING "Found AMD 8131 PCI-X tunnel, erraturm 
#63: ");
+            /* 0x7459 is AMD-8132 PCI-X IO-APIC */
+            else if ( vendor_id == 0x74591022 )
+                printk(XENLOG_WARNING "Found AMD 8132 PCI-X tunnel, erraturm 
#81: ");
+            else
+                continue;
+
+            if ( ioapic_ack_forced )
+            {
+                if ( ioapic_ack_new != 0 )
+                    printk("Not overriding command line. System will be 
unstable. "
+                           "Use ioapic_ack_mode=old\n");
+                else
+                    printk("Command line is ok for system stability\n");
+            }
+            else
+            {
+                printk("Forcing 'old' IO-APIC ack method\n");
+                ioapic_ack_new = 0;
+            }
+            return;
+        }
+    }
+}
+
 void __init setup_IO_APIC(void)
 {
+    amd813x_errata_quirks();
+
     enable_IO_APIC();
 
     if (acpi_ioapic)

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