Le 21/09/2018 à 12:26, Aneesh Kumar K.V a écrit :
On 9/21/18 11:25 AM, Christophe LEROY wrote:
Le 20/09/2018 à 20:09, Aneesh Kumar K.V a écrit :
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index d71c7777669c..aee04b209b51 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -188,11 +188,10 @@ void set_pte_at(struct mm_struct *mm, unsigned
long addr, pte_t *ptep,
pte_t pte)
{
/*
- * When handling numa faults, we already have the pte marked
- * _PAGE_PRESENT, but we can be sure that it is not in hpte.
- * Hence we can use set_pte_at for them.
+ * Make sure hardware valid bit is not set. We don't do
+ * tlb flush for this update.
*/
- VM_WARN_ON(pte_present(*ptep) && !pte_protnone(*ptep));
+ VM_WARN_ON(pte_val(*ptep) & _PAGE_PRESENT);
Why not using pte_present() anymore ?
Also, you are removing the pte_protnone() check, won't it change the
behaviour ?
If we can't use pte_present(), can we create a new helper for that
(allthough _PAGE_PRESENT exists on all platforms).
Christophe
This patch update a page table clear to clear _PAGE_PRESENT and mark it
invalid via _PAGE_INVALID. The pte_present now looks at both the flag.
That is we want these transient clear of pte to be considered as present
pte even if _PAGE_PRESENT is cleared. What we are catching by the debug
BUG_ON in these function is we are not using them to set a pte where the
old entry has a hadware valid bit set. This is because we don't do any
tlb flush with set_pte_at.
So the reason for pte_present -> pte_val() & _PAGE_PRESENT is because we
swtiched the clear to clear _PAGE_PRESENT and set _PAGE_INVALID and
pte_present now check both.
The reason for the removal of pte_protnone is because we dropped that
set_pte_at usage from core autonuma code long time back.
Now Considering we are calling this from mm/pgtable.c With your approach
of not using pte flags directly in core code we could switch this to
pte_hw_valid(). May be we can do that as an addon patch?
Ok, depending on which serie goes first, I'll add it in mine if I have
to rebase.
Christophe
