[PATCH 2/2] lguest: read offset of device_cap later

From: Paul Bolle
Date: Thu Mar 03 2016 - 07:01:54 EST


Read the offset of the capability with type VIRTIO_PCI_CAP_DEVICE_CFG
only when we're sure we're going to need it. Which is when all checks
have passed and we know we have a virtio console with an emerg_wr field.

Signed-off-by: Paul Bolle <pebolle@xxxxxxxxxx>
---
arch/x86/lguest/boot.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 535e3197d0c7..3b0c0eb4abf8 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1233,8 +1233,6 @@ static void write_bar_via_cfg(u32 cfg_offset, u32 off, u32 val)
static void probe_pci_console(void)
{
u8 cap, common_cap = 0, device_cap = 0;
- /* Offset within BAR0 */
- u32 device_offset;
u32 device_len;

/* Avoid recursive printk into here. */
@@ -1258,21 +1256,16 @@ 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;

type = read_pci_config_byte(0, 1, 0,
cap + offsetof(struct virtio_pci_cap, cfg_type));
bar = read_pci_config_byte(0, 1, 0,
cap + offsetof(struct virtio_pci_cap, bar));
- offset = read_pci_config(0, 1, 0,
- cap + offsetof(struct virtio_pci_cap, offset));

switch (type) {
case VIRTIO_PCI_CAP_DEVICE_CFG:
- if (bar == 0) {
+ if (bar == 0)
device_cap = cap;
- device_offset = offset;
- }
break;
case VIRTIO_PCI_CAP_PCI_CFG:
console_access_cap = cap;
@@ -1302,7 +1295,8 @@ static void probe_pci_console(void)
return;
}

- console_cfg_offset = device_offset;
+ console_cfg_offset = read_pci_config(0, 1, 0,
+ device_cap + offsetof(struct virtio_pci_cap, offset));
printk(KERN_INFO "lguest: Console via virtio-pci emerg_wr\n");
}

--
2.4.3