On Wed, 2014-10-01 at 15:13 +0530, Aneesh Kumar K.V wrote:

Michael Neuling [off-list ref] writes:
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quoted

From: Ian Munsie <redacted>

This adds a new function hash_page_mm() based on the existing hash_page=

().

quoted

This version allows any struct mm to be passed in, rather than assuming
current.  This is useful for servicing co-processor faults which are no=

t in the

quoted

context of the current running process.

We need to be careful here as the current hash_page() assumes current i=

n a few

quoted

places.

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It would be nice to document the rules here. So when we try to add a hash
page entry, and if that result in demotion of the segment are we suppose =

to

flush slbs ?=20

Yeah, we found it sucky to understand.  The current documentation is
"buy benh a beer and ask him" which doesn't scale very well unless
you're benh and you like beer.

Also why would one want to hash anything other
than current->mm ? How will this get called ?=20

We are calling this on behalf of a co-processor (eg cxl).  The mm this
is currently associated with may not be running on a cpu. =20

May be they are explained in later patches. But can we also explain it
here.=20

Ok, I'll add something (mpe had the same question).

Mikey

=20

quoted

Signed-off-by: Ian Munsie <redacted>
Signed-off-by: Michael Neuling <redacted>
---
 arch/powerpc/include/asm/mmu-hash64.h |  1 +
 arch/powerpc/mm/hash_utils_64.c       | 22 ++++++++++++++--------
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu-hash64.h b/arch/powerpc/inclu=

de/asm/mmu-hash64.h

quoted

index 6d0b7a2..f84e5a5 100644

--- a/arch/powerpc/include/asm/mmu-hash64.h
+++ b/arch/powerpc/include/asm/mmu-hash64.h

@@ -322,6 +322,7 @@ extern int __hash_page_64K(unsigned long ea, unsign=

ed long access,

quoted

 			   unsigned int local, int ssize);
 struct mm_struct;
 unsigned int hash_page_do_lazy_icache(unsigned int pp, pte_t pte, int =

trap);

quoted

+extern int hash_page_mm(struct mm_struct *mm, unsigned long ea, unsign=

ed long access, unsigned long trap);

quoted

 extern int hash_page(unsigned long ea, unsigned long access, unsigned =

long trap);

quoted

 int __hash_page_huge(unsigned long ea, unsigned long access, unsigned =

long vsid,

quoted

 		     pte_t *ptep, unsigned long trap, int local, int ssize,

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_uti=

ls_64.c

quoted

index bbdb054..0a5c8c0 100644

--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c

@@ -904,7 +904,7 @@ void demote_segment_4k(struct mm_struct *mm, unsign=

ed long addr)

quoted

 		return;
 	slice_set_range_psize(mm, addr, 1, MMU_PAGE_4K);
 	copro_flush_all_slbs(mm);
-	if (get_paca_psize(addr) !=3D MMU_PAGE_4K) {
+	if ((get_paca_psize(addr) !=3D MMU_PAGE_4K) && (current->mm =3D=3D mm=

)) {

quoted

 		get_paca()->context =3D mm->context;
 		slb_flush_and_rebolt();
 	}

@@ -989,26 +989,24 @@ static void check_paca_psize(unsigned long ea, st=

ruct mm_struct *mm,

quoted

  * -1 - critical hash insertion error
  * -2 - access not permitted by subpage protection mechanism
  */
-int hash_page(unsigned long ea, unsigned long access, unsigned long tr=

ap)

quoted

+int hash_page_mm(struct mm_struct *mm, unsigned long ea, unsigned long=

 access, unsigned long trap)

quoted

 {
 	enum ctx_state prev_state =3D exception_enter();
 	pgd_t *pgdir;
 	unsigned long vsid;
-	struct mm_struct *mm;
 	pte_t *ptep;
 	unsigned hugeshift;
 	const struct cpumask *tmp;
 	int rc, user_region =3D 0, local =3D 0;
 	int psize, ssize;
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-	DBG_LOW("hash_page(ea=3D%016lx, access=3D%lx, trap=3D%lx\n",
-		ea, access, trap);
+	DBG_LOW("%s(ea=3D%016lx, access=3D%lx, trap=3D%lx\n",
+		__func__, ea, access, trap);
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 	/* Get region & vsid */
  	switch (REGION_ID(ea)) {
 	case USER_REGION_ID:
 		user_region =3D 1;
-		mm =3D current->mm;
 		if (! mm) {
 			DBG_LOW(" user region with no mm !\n");
 			rc =3D 1;

@@ -1104,7 +1102,8 @@ int hash_page(unsigned long ea, unsigned long acc=

ess, unsigned long trap)

quoted

 			WARN_ON(1);
 		}
 #endif
-		check_paca_psize(ea, mm, psize, user_region);
+		if (current->mm =3D=3D mm)
+			check_paca_psize(ea, mm, psize, user_region);
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 		goto bail;
 	}

@@ -1145,7 +1144,8 @@ int hash_page(unsigned long ea, unsigned long acc=

ess, unsigned long trap)

quoted

 		}
 	}
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-	check_paca_psize(ea, mm, psize, user_region);
+	if (current->mm =3D=3D mm)
+		check_paca_psize(ea, mm, psize, user_region);
 #endif /* CONFIG_PPC_64K_PAGES */
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 #ifdef CONFIG_PPC_HAS_HASH_64K

@@ -1180,6 +1180,12 @@ bail:
 	exception_exit(prev_state);
 	return rc;
 }
+EXPORT_SYMBOL_GPL(hash_page_mm);
+
+int hash_page(unsigned long ea, unsigned long access, unsigned long tr=

ap)

quoted

+{
+	return hash_page_mm(current->mm, ea, access, trap);
+}
 EXPORT_SYMBOL_GPL(hash_page);
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 void hash_preload(struct mm_struct *mm, unsigned long ea,
--=20
1.9.1

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