[GIT PULL v2] EFI urgent fix

[GIT PULL v2] EFI urgent fix

[Matt Fleming]

Folks, please pull the following with from Wang which includes a
rewritten changelog as compared with the previous pull request.

The following changes since commit 04974df8049fc4240d22759a91e035082ccd18b4:

  Linux 4.6-rc6 (2016-05-01 15:52:31 -0700)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi.git tags/efi-urgent

for you to fetch changes up to 8491332837eed61cd5d47613b33cba90b809f36a:

  x86/sysfb_efi: Fix valid BAR address range check (2016-05-05 13:14:04 +0100)

----------------------------------------------------------------
 * Fix sysfb_efi to detect BARs starting at 0x0, which otherwise makes
   video=efifb not work on some the ThinkPad E550 - Wang YanQing

----------------------------------------------------------------
Wang YanQing (1):
      x86/sysfb_efi: Fix valid BAR address range check

 arch/x86/kernel/sysfb_efi.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

[PATCH] x86/sysfb_efi: Fix valid BAR address range check

[Matt Fleming]

From: Wang YanQing <udknight@gmail.com>

The code for checking whether a BAR address range is valid will break
out of the loop when a start address of 0x0 is encountered.

This behaviour is wrong since by breaking out of the loop we may miss
the BAR that describes the EFI frame buffer in a later iteration.

Because of this bug I can't use video=efifb: boot parameter to get
efifb on my new ThinkPad E550 for my old linux system hard disk with
3.10 kernel. In 3.10, efifb is the only choice due to DRM/I915 not
supporting the GPU.

This patch also add a trivial optimization to break out after we find
the frame buffer address range without testing later BARs.

Signed-off-by: Wang YanQing <udknight@gmail.com>
Reviewed-by: Peter Jones <pjones@redhat.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: <stable@vger.kernel.org>
[ Rewrote changelog. ]
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
---
 arch/x86/kernel/sysfb_efi.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/sysfb_efi.c b/arch/x86/kernel/sysfb_efi.c
index b285d4e8c68e..5da924bbf0a0 100644
--- a/arch/x86/kernel/sysfb_efi.c
+++ b/arch/x86/kernel/sysfb_efi.c
@@ -106,14 +106,24 @@ static int __init efifb_set_system(const struct dmi_system_id *id)
 					continue;
 				for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
 					resource_size_t start, end;
+					unsigned long flags;
+
+					flags = pci_resource_flags(dev, i);
+					if (!(flags & IORESOURCE_MEM))
+						continue;
+
+					if (flags & IORESOURCE_UNSET)
+						continue;
+
+					if (pci_resource_len(dev, i) == 0)
+						continue;
 
 					start = pci_resource_start(dev, i);
-					if (start == 0)
-						break;
 					end = pci_resource_end(dev, i);
 					if (screen_info.lfb_base >= start &&
 					    screen_info.lfb_base < end) {
 						found_bar = 1;
+						break;
 					}
 				}
 			}
-- 
2.7.3