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powerpc/mm/subpage: Initialise user psize correctly

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As part of the radix support we switched Book3s64 to use a value of ~0
for MMU_NO_CONTEXT. That is because id 0 is special on radix.

However that broke the logic in init_new_context(). The code there needs
to differentiate between a newly allocated context and one inherited via
fork. Previously it worked because a newly allocated context has an id
of zero (because it was just memset() to zero), which used to match
MMU_NO_CONTEXT, and therefore slice_mm_new_context() did the right
thing.

Instead check against a context.id value of zero instead of using
slice_mm_new_context().

Without this patch we never call slice_set_user_psize(), and end up with
a slice psize value of zero and we always end up using 4K HPTE.

Fixes: 1a472c9dba ("powerpc/mm/radix: Add tlbflush routines")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Aneesh Kumar K.V 2016-05-02 16:21:50 +05:30 committed by Michael Ellerman
parent bb03efe2b7
commit 2d566537dd
1 changed files with 10 additions and 1 deletions
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11
arch/powerpc/mm/mmu_context_book3s64.c
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@ -85,8 +85,17 @@ int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
/* The old code would re-promote on fork, we don't do that
* when using slices as it could cause problem promoting slices
* that have been forced down to 4K
*
* For book3s we have MMU_NO_CONTEXT set to be ~0. Hence check
* explicitly against context.id == 0. This ensures that we
* properly initialize context slice details for newly allocated
* mm's (which will have id == 0) and don't alter context slice
* inherited via fork (which will have id != 0).
*
* We should not be calling init_new_context() on init_mm. Hence a
* check against 0 is ok.
*/
if (slice_mm_new_context(mm))
if (mm->context.id == 0)
slice_set_user_psize(mm, mmu_virtual_psize);
subpage_prot_init_new_context(mm);
}