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[Qemu-devel] sh: dcache flush breaks text region?
From: |
Shin-ichiro KAWASAKI |
Subject: |
[Qemu-devel] sh: dcache flush breaks text region? |
Date: |
Sun, 11 Jan 2009 02:38:48 +0900 |
User-agent: |
Thunderbird 2.0.0.19 (Windows/20081209) |
Hi, all.
I'm now working on to expand qemu-sh to emulate
"Solution Engine 7750", and found one odd thing.
Could you give me some advice?
My SH7750 emulation environment fails to boot up.
I made some investigation and found that,
- the linux kernel for SE7750(se7750_defconfig) flushes
dcache on its boot sequence.
- SH7750's dcache is 16KB and direct-map.
Then 16KB memory region are touched and modified to flush it.
- empty_zero_page is used for this flush, but it only has
4KB. The text region after it has got broken and causes
boot failure.
I added a patch against linux kernel to this mail for a reference.
It only reduces the flush region size to 4KB=PAGE_SIZE, but avoids
the problem and let the kernel boot up cleanly.
Of course it is not a good solution, because it does not flush all
caches.
I wonder two points.
- Does this problem happen on real SE7750 board?
In other words, does the current linux kernel work on it?
I don't have it, and can't check it out by myself.
- How should I solve the problem?
16KB region should be allocated for flush by kernel?
The patches for SE7750 emulation is not yet posted
to qemu-devel. Before it, I'd like to solve the problem.
Any comments will be appreciated.
Regards,
Shin-ichiro KAWASAKI
diff --git a/arch/sh/mm/cache-sh4.c b/arch/sh/mm/cache-sh4.c
index 5cfe08d..4042c8c 100644
--- a/arch/sh/mm/cache-sh4.c
+++ b/arch/sh/mm/cache-sh4.c
@@ -612,6 +612,9 @@ static void __flush_dcache_segment_1way(unsigned long start,
a0 = base_addr;
a0e = base_addr + extent_per_way;
+ if (a0e > ((unsigned long)&empty_zero_page[0]) + PAGE_SIZE) {
+ a0e = ((unsigned long)&empty_zero_page[0]) + PAGE_SIZE;
+ }
do {
asm volatile("ldc %0, sr" : : "r" (sr_with_bl));
asm volatile("movca.l r0, @%0\n\t"
- [Qemu-devel] sh: dcache flush breaks text region?,
Shin-ichiro KAWASAKI <=