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[tip:x86/cleanups] lguest: Read length of device_cap later

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  [tip:x86/cleanups] lguest: Read length of device_cap later tip-bot for Paul Bolle <tipbot@zytor.com> - 2016-06-10 11:50 +0200

#1419170 — [tip:x86/cleanups] lguest: Read length of device_cap later

Commit-ID:  7faf90ef995ea470f32f43810266ece8ac8ba6c7
Gitweb:     http://git.kernel.org/tip/7faf90ef995ea470f32f43810266ece8ac8ba6c7
Author:     Paul Bolle <pebolle@tiscali.nl>
AuthorDate: Thu, 3 Mar 2016 13:01:40 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 10 Jun 2016 11:39:09 +0200

lguest: Read length of device_cap later

Read the length of the capability with type VIRTIO_PCI_CAP_DEVICE_CFG
only when we're sure we're going to need it. Which is just before the
check whether the virtio console actually has an emerg_wr field.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: lguest@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1457006501-5377-2-git-send-email-pebolle@tiscali.nl
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 arch/x86/lguest/boot.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 3847e73..146d11c 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1258,7 +1258,7 @@ static void probe_pci_console(void)
 		u8 vndr = read_pci_config_byte(0, 1, 0, cap);
 		if (vndr == PCI_CAP_ID_VNDR) {
 			u8 type, bar;
-			u32 offset, length;
+			u32 offset;
 
 			type = read_pci_config_byte(0, 1, 0,
 			    cap + offsetof(struct virtio_pci_cap, cfg_type));
@@ -1266,15 +1266,12 @@ static void probe_pci_console(void)
 			    cap + offsetof(struct virtio_pci_cap, bar));
 			offset = read_pci_config(0, 1, 0,
 			    cap + offsetof(struct virtio_pci_cap, offset));
-			length = read_pci_config(0, 1, 0,
-			    cap + offsetof(struct virtio_pci_cap, length));
 
 			switch (type) {
 			case VIRTIO_PCI_CAP_DEVICE_CFG:
 				if (bar == 0) {
 					device_cap = cap;
 					device_offset = offset;
-					device_len = length;
 				}
 				break;
 			case VIRTIO_PCI_CAP_PCI_CFG:
@@ -1297,6 +1294,8 @@ static void probe_pci_console(void)
 	 * emerg_wr.  If it doesn't support VIRTIO_CONSOLE_F_EMERG_WRITE
 	 * it should ignore the access.
 	 */
+	device_len = read_pci_config(0, 1, 0,
+			device_cap + offsetof(struct virtio_pci_cap, length));
 	if (device_len < (offsetof(struct virtio_console_config, emerg_wr)
 			  + sizeof(u32))) {
 		printk(KERN_ERR "lguest: console missing emerg_wr field\n");

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