x86, mrst: use a temporary variable for SFI irq

SFI tables reside in RAM and should not be modified once they are
written.  Current code went to set pentry->irq to zero which causes
subsequent reads to fail with invalid SFI table checksum.  This will
break kexec as the second kernel fails to validate SFI tables.

To fix this we use temporary variable for irq number.
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/x86/platform/mrst/mrst.c

@@ -678,38 +678,40 @@ static int __init sfi_parse_devs(struct sfi_table_header *table)
 	pentry = (struct sfi_device_table_entry *)sb->pentry;
 
 	for (i = 0; i < num; i++, pentry++) {
-		if (pentry->irq != (u8)0xff) { /* native RTE case */
+		int irq = pentry->irq;
+
+		if (irq != (u8)0xff) { /* native RTE case */
 			/* these SPI2 devices are not exposed to system as PCI
 			 * devices, but they have separate RTE entry in IOAPIC
 			 * so we have to enable them one by one here
 			 */
-			ioapic = mp_find_ioapic(pentry->irq);
+			ioapic = mp_find_ioapic(irq);
 			irq_attr.ioapic = ioapic;
-			irq_attr.ioapic_pin = pentry->irq;
+			irq_attr.ioapic_pin = irq;
 			irq_attr.trigger = 1;
 			irq_attr.polarity = 1;
-			io_apic_set_pci_routing(NULL, pentry->irq, &irq_attr);
+			io_apic_set_pci_routing(NULL, irq, &irq_attr);
 		} else
-			pentry->irq = 0; /* No irq */
+			irq = 0; /* No irq */
 
 		switch (pentry->type) {
 		case SFI_DEV_TYPE_IPC:
 			/* ID as IRQ is a hack that will go away */
-			pdev = platform_device_alloc(pentry->name, pentry->irq);
+			pdev = platform_device_alloc(pentry->name, irq);
 			if (pdev == NULL) {
 				pr_err("out of memory for SFI platform device '%s'.\n",
 							pentry->name);
 				continue;
 			}
-			install_irq_resource(pdev, pentry->irq);
+			install_irq_resource(pdev, irq);
 			pr_debug("info[%2d]: IPC bus, name = %16.16s, "
-				"irq = 0x%2x\n", i, pentry->name, pentry->irq);
+				"irq = 0x%2x\n", i, pentry->name, irq);
 			sfi_handle_ipc_dev(pdev);
 			break;
 		case SFI_DEV_TYPE_SPI:
 			memset(&spi_info, 0, sizeof(spi_info));
 			strncpy(spi_info.modalias, pentry->name, SFI_NAME_LEN);
-			spi_info.irq = pentry->irq;
+			spi_info.irq = irq;
 			spi_info.bus_num = pentry->host_num;
 			spi_info.chip_select = pentry->addr;
 			spi_info.max_speed_hz = pentry->max_freq;
@@ -726,7 +728,7 @@ static int __init sfi_parse_devs(struct sfi_table_header *table)
 			memset(&i2c_info, 0, sizeof(i2c_info));
 			bus = pentry->host_num;
 			strncpy(i2c_info.type, pentry->name, SFI_NAME_LEN);
-			i2c_info.irq = pentry->irq;
+			i2c_info.irq = irq;
 			i2c_info.addr = pentry->addr;
 			pr_debug("info[%2d]: I2C bus = %d, name = %16.16s, "
 				"irq = 0x%2x, addr = 0x%x\n", i, bus,