Andi Kleen wrote:
Yeah, that may be true, but this particular tree is weird, and I'm trying
to understand what's going on here. Specifically, 64-bit ioremap()s
*don't* set _PAGE_GLOBAL, which appears to be an accident resulting from
the strange definitions of __PAGE_KERNEL_* vs PAGE_KERNEL_*.
ioremap() should set G agreed.
For example, ioremap_64.c:__ioremap() creates a vma for the io mapping, and
explicitly sets _PAGE_GLOBAL in the vma's version of pgprot - but then it
calls ioremap_page_range() to actually create the mapping, which ends up
making a non-global mapping, because its rolling its own version of
PAGE_KERNEL by using pgprot(__PAGE_KERNEL) - which is not the actual
definition of PAGE_KERNEL.
That should not really matter because ioremap_change_attr()->c_p_a is only
called
when flags is != 0 and that means it is already different from PAGE_KERNEL.
I think there's a bug around here, but I think its currently being hidden
There's one Jan pointed out: iounmap does not subtract the guard page size
so it ends up resetting one page too much. That is probably what causes your
problem. But again you should be passing in G in the first place.
-Andi
Here was Jan's patch; it incidently fixes the G problem too
OK, great. Ingo, that means we can use this and go back to folding
_PAGE_GLOBAL into __PAGE_KERNEL_*. Well, at least give it a try.
J
snip
Additionally I found it necessary to fix ioremap_64.c's use of
change_page_attr_addr():
--- a/arch/x86/mm/ioremap_64.c
+++ b/arch/x86/mm/ioremap_64.c
@@ -48,7 +48,7 @@ ioremap_change_attr(unsigned long phys_a
* Must use a address here and not struct page because the phys
addr
* can be a in hole between nodes and not have an memmap entry.
*/
- err =
change_page_attr_addr(vaddr,npages,__pgprot(__PAGE_KERNEL|flags));
+ err =
change_page_attr_addr(vaddr,npages,MAKE_GLOBAL(__PAGE_KERNEL|flags));
if (!err)
global_flush_tlb();
}
@@ -199,7 +199,7 @@ void iounmap(volatile void __iomem *addr
/* Reset the direct mapping. Can block */
if (p->flags >> 20)
- ioremap_change_attr(p->phys_addr, p->size, 0);
+ ioremap_change_attr(p->phys_addr, get_vm_area_size(p), 0);
/* Finally remove it */
o = remove_vm_area((void *)addr);
Other extra changes I had in my version could possibly be counted as
enhancements...
Jan
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