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Subjectaperture_64.c: duplicated code, buggy?
Hi!

void __init early_gart_iommu_check(void)

contains

for (num = 24; num < 32; num++) {
if (!early_is_k8_nb(read_pci_config(0, num, 3, 0x00)))
continue;
loop, with very similar loop duplicated in

void __init gart_iommu_hole_init(void)

. First copy of a loop seems to be buggy, too. It uses 0 as a "nothing
set" value, which may actually bite us in last_aper_enabled case
(because it may be often zero).

(Beware, it is hard to test this patch, because this code has about
2^8 different code paths, depending on hardware and cmdline settings).

Plus, the second loop does not check for consistency of
aper_enabled. Should it?

---
early_gart_iommu_check(void) uses 0 as a "nothing set" value, which
may actually bite us in last_aper_enabled case (because it may be
often zero).

Signed-off-by: Pavel Machek <pavel@suse.cz>

diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
index 4a3d8cf..2088b6a 100644
--- a/arch/x86/kernel/aperture_64.c
+++ b/arch/x86/kernel/aperture_64.c
@@ -241,11 +242,12 @@ void __init early_gart_iommu_check(void)
u32 ctl;
u32 aper_size = 0, aper_order = 0, last_aper_order = 0;
u64 aper_base = 0, last_aper_base = 0;
- int aper_enabled = 0, last_aper_enabled = 0;
+ int aper_enabled = 0, last_aper_enabled = 0, last_valid = 0;

if (!early_pci_allowed())
return;

+ /* This is mostly duplicate of iommu_hole_init */
fix = 0;
for (num = 24; num < 32; num++) {
if (!early_is_k8_nb(read_pci_config(0, num, 3, 0x00)))
@@ -258,15 +260,17 @@ void __init early_gart_iommu_check(void)
aper_base = read_pci_config(0, num, 3, AMD64_GARTAPERTUREBASE) & 0x7fff;
aper_base <<= 25;

- if ((last_aper_order && aper_order != last_aper_order) ||
- (last_aper_base && aper_base != last_aper_base) ||
- (last_aper_enabled && aper_enabled != last_aper_enabled)) {
- fix = 1;
- break;
- }
+ if (last_valid)
+ if ((aper_order != last_aper_order) ||
+ (aper_base != last_aper_base) ||
+ (aper_enabled != last_aper_enabled)) {
+ fix = 1;
+ break;
+ }
last_aper_order = aper_order;
last_aper_base = aper_base;
last_aper_enabled = aper_enabled;
+ last_valid = 1;
}

if (!fix && !aper_enabled)

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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