Hi Michael,
On Mon, May 14, 2018 at 1:10 PM, Michael Schmitz <schmitzmic@xxxxxxxxx> wrote:
On kernels with 020/030 support ...
get_io_area leaves an IO_SIZE gap between mappings which is added to
the vm_struct representing the mapping. __ioremap() uses the actual
requested size (after alignment), while __iounmap() is passed the
size from the vm_struct.
On 020/030, early termination descriptors are used to set up mappings of
extent 'size', which are validated on unmapping. The unmapped gap of size
IO_SIZE defeats the sanity check of the pmd tables, causing __iounmap to
loop forever on 030.
On 040/040, unmapping of page table entries does not check for a valid
040/060
mapping, so the umapping loop always completes there.
Adjust size to be unmapped by the gap that had been added in the vm_struct
prior.
This fixes the hang in atari_platform_init() reported a long time ago, and
a similar one reported by Finn recently (addressed by removing ioremap()
use from the SWIM driver.
Tested on my Falcon in 030 mode - untested but should work the same on
040/060 (the extra page tables cleared there would never have been set up
anyway).
Comment on whether the gap size should be considered in looking for a
suitable address to place the next mapping in get_io_area() would be welcome.
At first sight (and looking in full-history-linux git history), I see no
reason for the gap. I'd assume having a block with address and size aligned
to 256 KiB (which the caller already takes care of: IO_SIZE is 256 KiB if
020/030 support is enabled) should be sufficient to use early termination
tables.
Obviously removing the gap would fix the issue as well, but that's more
risky...
Signed-off-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
---
arch/m68k/mm/kmap.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/arch/m68k/mm/kmap.c b/arch/m68k/mm/kmap.c
index c2a3832..3b420f6 100644
--- a/arch/m68k/mm/kmap.c
+++ b/arch/m68k/mm/kmap.c
@@ -89,7 +89,8 @@ static inline void free_io_area(void *addr)
for (p = &iolist ; (tmp = *p) ; p = &tmp->next) {
if (tmp->addr == addr) {
*p = tmp->next;
- __iounmap(tmp->addr, tmp->size);
+ /* remove gap added in get_io_area() */
+ __iounmap(tmp->addr, tmp->size - IO_SIZE);
kfree(tmp);
return;
}
Looks good to me, so I will apply and queue for v4.18 with the patch
description slightly modified, but will wait one more day, in case someone
has a comment.
Thanks a lot!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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