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powerpc/mm/books3s: Add new pte bit to mark pte temporarily invalid.

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When splitting a huge pmd pte, we need to mark the pmd entry invalid. We
can do that by clearing _PAGE_PRESENT bit. But then that will be taken as a
swap pte. In order to differentiate between the two use a software pte bit
when invalidating.

For regular pte, due to bd5050e38a ("powerpc/mm/radix: Change pte relax
sequence to handle nest MMU hang") we need to mark the pte entry invalid when
relaxing access permission. Instead of marking pte_none which can result in
different page table walk routines possibly skipping this pte entry, invalidate
it but still keep it marked present.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Aneesh Kumar K.V 2018-08-22 22:46:04 +05:30 committed by Michael Ellerman
parent 810e9f86f3
commit bd0dbb73e0
1 changed files with 17 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

18
arch/powerpc/include/asm/book3s/64/pgtable.h
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@ -44,6 +44,16 @@
#define _PAGE_PTE 0x4000000000000000UL /* distinguishes PTEs from pointers */
#define _PAGE_PRESENT 0x8000000000000000UL /* pte contains a translation */
/*
* We need to mark a pmd pte invalid while splitting. We can do that by clearing
* the _PAGE_PRESENT bit. But then that will be taken as a swap pte. In order to
* differentiate between two use a SW field when invalidating.
*
* We do that temporary invalidate for regular pte entry in ptep_set_access_flags
*
* This is used only when _PAGE_PRESENT is cleared.
*/
#define _PAGE_INVALID _RPAGE_SW0
/*
* Top and bottom bits of RPN which can be used by hash
@ -568,7 +578,13 @@ static inline pte_t pte_clear_savedwrite(pte_t pte)
static inline int pte_present(pte_t pte)
{
return !!(pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT));
/*
* A pte is considerent present if _PAGE_PRESENT is set.
* We also need to consider the pte present which is marked
* invalid during ptep_set_access_flags. Hence we look for _PAGE_INVALID
* if we find _PAGE_PRESENT cleared.
*/
return !!(pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_INVALID));
}
#ifdef CONFIG_PPC_MEM_KEYS