Re: [RFC PATCH] powerpc/book3s/hash: Drop _PAGE_PRIVILEGED from PAGE_NONE
On 11/13/23 5:17 PM, Nicholas Piggin wrote:
> On Mon Nov 13, 2023 at 8:45 PM AEST, Aneesh Kumar K V wrote:
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c
b/arch/powerpc/mm/book3s64/hash_utils.c
index ad2afa08e62e..b2eda22195f0 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -310,9 +310,26 @@ unsigned long htab_convert_pte_flags(unsigned long
pteflags, unsigned long flags
else
rflags |= 0x3;
}
+ WARN_ON(!(pteflags & _PAGE_RWX));
} else {
if (pteflags & _PAGE_RWX)
rflags |= 0x2;
+ else {
+ /*
+ * PAGE_NONE will get mapped to 0b110 (slb key 1 no
access)
+ * We picked 0b110 instead of 0b000 so that slb key 0
will
+ * get only read only access for the same rflags.
+ */
+ if (mmu_has_feature(MMU_FTR_KERNEL_RO))
+ rflags |= (HPTE_R_PP0 | 0x2);
+ /*
+ * rflags = HPTE_R_N
+ * Without KERNEL_RO feature this will result in slb
+ * key 0 with read/write. But ISA only supports that.
+ * There is no key 1 no-access and key 0 read-only
+ * pp bit support.
+ */
+ }
if (!((pteflags & _PAGE_WRITE) && (pteflags & _PAGE_DIRTY)))
rflags |= 0x1;
}
>>>
>>
>> V2 is also dropping the above change, because we will never have hash table
>> entries inserted.
>>
>> This is added to commit message.
>>
>> Hash fault handling code did get some WARN_ON added because those
>> functions are not expected to get called with _PAGE_READ cleared.
>> commit 18061c17c8ec ("powerpc/mm: Update PROTFAULT handling in the page
>> fault path")
>> explains the details.
>
> Should it be a WARN_ON_ONCE? Any useful way to recover from it? Could
> the added WARN come with some comments from that commit that explain
> it?
>
This should never happen unless someone messed up check_pte_access(). The
WARN_ON() is a way
to remind me not to add no access ppp mapping in the htab_convert_pte_flags()
as I did above.
Initially I was planning to add only a comment, but then in the rare case of we
getting it wrong
it is nice to do a console log.
-aneesh
Re: [RFC PATCH] powerpc/book3s/hash: Drop _PAGE_PRIVILEGED from PAGE_NONE
On Mon Nov 13, 2023 at 8:45 PM AEST, Aneesh Kumar K V wrote:
> On 11/13/23 3:46 PM, Nicholas Piggin wrote:
> > On Thu Nov 2, 2023 at 11:23 PM AEST, Aneesh Kumar K.V wrote:
> >> There used to be a dependency on _PAGE_PRIVILEGED with pte_savedwrite.
> >> But that got dropped by
> >> commit 6a56ccbcf6c6 ("mm/autonuma: use can_change_(pte|pmd)_writable() to
> >> replace savedwrite")
> >>
> >> With this change numa fault pte (pte_protnone()) gets mapped as regular
> >> user pte
> >> with RWX cleared (no-access).
> >
> > You mean "that" above change (not *this* change), right?
> >
>
> With the change in this patch numa fault pte will not have _PAGE_PRIVILEGED
> set because
> PAGE_NONE now maps to just _PAGE_BASE
Right, I guess I was confused because I missed the pgtable-mask.h move.
> >> This also remove pte_user() from
> >> book3s/64.
> >
> > Nice cleanup. That was an annoying hack.
> >
> >> pte_access_permitted() now checks for _PAGE_EXEC because we now support
> >> EXECONLY mappings.
> >
> > AFAIKS pte_exec() is not required, GUP is really only for read or
> > write access. It should be a separate patch if you think it's needed.
> >
>
> I have a v2 dropping that based on
> https://lore.kernel.org/linux-mm/87bkc1oe8c@linux.ibm.com
> I kept pte_user with pte_access_permitted being the only user. I can open
> code that
> if needed.
I don't mind keeping pte_user() and the check in pte_access_permitted().
> >>
> >> Signed-off-by: Aneesh Kumar K.V
> >> ---
> >> arch/powerpc/include/asm/book3s/64/pgtable.h | 23 +---
> >> arch/powerpc/mm/book3s64/hash_utils.c| 17 +++
> >> 2 files changed, 23 insertions(+), 17 deletions(-)
> >>
> >> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h
> >> b/arch/powerpc/include/asm/book3s/64/pgtable.h
> >> index cb77eddca54b..7c7de7b56df0 100644
> >> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> >> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> >> @@ -17,12 +17,6 @@
> >> #define _PAGE_EXEC0x1 /* execute permission */
> >> #define _PAGE_WRITE 0x2 /* write access allowed */
> >> #define _PAGE_READ0x4 /* read access allowed */
> >> -#define _PAGE_NA _PAGE_PRIVILEGED
> >> -#define _PAGE_NAX _PAGE_EXEC
> >> -#define _PAGE_RO _PAGE_READ
> >> -#define _PAGE_ROX (_PAGE_READ | _PAGE_EXEC)
> >> -#define _PAGE_RW (_PAGE_READ | _PAGE_WRITE)
> >> -#define _PAGE_RWX (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC)
> >> #define _PAGE_PRIVILEGED 0x8 /* kernel access only */
> >> #define _PAGE_SAO 0x00010 /* Strong access order */
> >> #define _PAGE_NON_IDEMPOTENT 0x00020 /* non idempotent memory */
> >
> > Did you leave PAGE_NONE as _PAGE_BASE | _PAGE_PRIVILEGED below?
> > Shouldn't that be changed too? Then this patch is not only hash
> > but also radix.
> >
>
> A recent patch moved PAGE_NONE to pgtable-mask.h
> a5a08dc90f4513d1a78582ec24b687fad01cc843
Thanks I did miss it.
>
> > Why is the hash change required? Previously PAGE_NONE relied on
> > privileged bit to prevent access, now you need to handle a PTE
> > without that bit? In that case could that be patch 1, then the
> > rest patch 2?
> >
>
> Looking at older kernel, I guess check_pte_access used _PAGE_PRIVILEGED
> as a way to prevent access to PAGE_NONE ptes. We now depend on
> _PAGE_READ
>
> > __pte_flags_need_flush() should be updated after this too,
> > basically revert commit 1abce0580b894.
> >
>
> Will update the patch to include the revert.
>
> >> @@ -119,9 +113,9 @@
> >> /*
> >> * user access blocked by key
> >> */
> >> -#define _PAGE_KERNEL_RW (_PAGE_PRIVILEGED | _PAGE_RW |
> >> _PAGE_DIRTY)
> >> #define _PAGE_KERNEL_RO(_PAGE_PRIVILEGED | _PAGE_READ)
> >> #define _PAGE_KERNEL_ROX (_PAGE_PRIVILEGED | _PAGE_READ | _PAGE_EXEC)
> >> +#define _PAGE_KERNEL_RW (_PAGE_PRIVILEGED | _PAGE_RW |
> >> _PAGE_DIRTY)
> >> #define _PAGE_KERNEL_RWX (_PAGE_PRIVILEGED | _PAGE_DIRTY | _PAGE_RW |
> >> _PAGE_EXEC)
> >> /*
> >> * _PAGE_CHG_MASK masks of bits that are to be preserved across
> >
> > No need to reorder defines.
> >
>
> ok
>
>
> > Thanks,
> > Nick
> >
> >> @@ -523,19 +517,14 @@ static inline bool arch_pte_access_permitted(u64
> >> pte, bool write, bool execute)
> >> }
> >> #endif /* CONFIG_PPC_MEM_KEYS */
> >>
> >> -static inline bool pte_user(pte_t pte)
> >> -{
> >> - return !(pte_raw(pte) & cpu_to_be64(_PAGE_PRIVILEGED));
> >> -}
> >> -
> >> #define pte_access_permitted pte_access_permitted
> >> static inline bool pte_access_permitted(pte_t pte, bool write)
> >> {
> >> - /*
> >> - * _PAGE_READ is needed for any access and will be
> >> - * cleared for PROT_NONE
> >> - */
> >> - if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte))
> >> +
> >> + if (!pte_present(pte))
> >> + return false;
> >> +
> >> + if (!(pte_read(pte) || pte_exec(pte)))
> >>
Re: [RFC PATCH] powerpc/book3s/hash: Drop _PAGE_PRIVILEGED from PAGE_NONE
On 11/13/23 3:46 PM, Nicholas Piggin wrote:
> On Thu Nov 2, 2023 at 11:23 PM AEST, Aneesh Kumar K.V wrote:
>> There used to be a dependency on _PAGE_PRIVILEGED with pte_savedwrite.
>> But that got dropped by
>> commit 6a56ccbcf6c6 ("mm/autonuma: use can_change_(pte|pmd)_writable() to
>> replace savedwrite")
>>
>> With this change numa fault pte (pte_protnone()) gets mapped as regular user
>> pte
>> with RWX cleared (no-access).
>
> You mean "that" above change (not *this* change), right?
>
With the change in this patch numa fault pte will not have _PAGE_PRIVILEGED set
because
PAGE_NONE now maps to just _PAGE_BASE
>> This also remove pte_user() from
>> book3s/64.
>
> Nice cleanup. That was an annoying hack.
>
>> pte_access_permitted() now checks for _PAGE_EXEC because we now support
>> EXECONLY mappings.
>
> AFAIKS pte_exec() is not required, GUP is really only for read or
> write access. It should be a separate patch if you think it's needed.
>
I have a v2 dropping that based on
https://lore.kernel.org/linux-mm/87bkc1oe8c@linux.ibm.com
I kept pte_user with pte_access_permitted being the only user. I can open code
that
if needed.
>>
>> Signed-off-by: Aneesh Kumar K.V
>> ---
>> arch/powerpc/include/asm/book3s/64/pgtable.h | 23 +---
>> arch/powerpc/mm/book3s64/hash_utils.c| 17 +++
>> 2 files changed, 23 insertions(+), 17 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> index cb77eddca54b..7c7de7b56df0 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> @@ -17,12 +17,6 @@
>> #define _PAGE_EXEC 0x1 /* execute permission */
>> #define _PAGE_WRITE 0x2 /* write access allowed */
>> #define _PAGE_READ 0x4 /* read access allowed */
>> -#define _PAGE_NA_PAGE_PRIVILEGED
>> -#define _PAGE_NAX _PAGE_EXEC
>> -#define _PAGE_RO_PAGE_READ
>> -#define _PAGE_ROX (_PAGE_READ | _PAGE_EXEC)
>> -#define _PAGE_RW(_PAGE_READ | _PAGE_WRITE)
>> -#define _PAGE_RWX (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC)
>> #define _PAGE_PRIVILEGED0x8 /* kernel access only */
>> #define _PAGE_SAO 0x00010 /* Strong access order */
>> #define _PAGE_NON_IDEMPOTENT0x00020 /* non idempotent memory */
>
> Did you leave PAGE_NONE as _PAGE_BASE | _PAGE_PRIVILEGED below?
> Shouldn't that be changed too? Then this patch is not only hash
> but also radix.
>
A recent patch moved PAGE_NONE to pgtable-mask.h
a5a08dc90f4513d1a78582ec24b687fad01cc843
> Why is the hash change required? Previously PAGE_NONE relied on
> privileged bit to prevent access, now you need to handle a PTE
> without that bit? In that case could that be patch 1, then the
> rest patch 2?
>
Looking at older kernel, I guess check_pte_access used _PAGE_PRIVILEGED
as a way to prevent access to PAGE_NONE ptes. We now depend on
_PAGE_READ
> __pte_flags_need_flush() should be updated after this too,
> basically revert commit 1abce0580b894.
>
Will update the patch to include the revert.
>> @@ -119,9 +113,9 @@
>> /*
>> * user access blocked by key
>> */
>> -#define _PAGE_KERNEL_RW (_PAGE_PRIVILEGED | _PAGE_RW |
>> _PAGE_DIRTY)
>> #define _PAGE_KERNEL_RO (_PAGE_PRIVILEGED | _PAGE_READ)
>> #define _PAGE_KERNEL_ROX (_PAGE_PRIVILEGED | _PAGE_READ | _PAGE_EXEC)
>> +#define _PAGE_KERNEL_RW (_PAGE_PRIVILEGED | _PAGE_RW |
>> _PAGE_DIRTY)
>> #define _PAGE_KERNEL_RWX(_PAGE_PRIVILEGED | _PAGE_DIRTY | _PAGE_RW |
>> _PAGE_EXEC)
>> /*
>> * _PAGE_CHG_MASK masks of bits that are to be preserved across
>
> No need to reorder defines.
>
ok
> Thanks,
> Nick
>
>> @@ -523,19 +517,14 @@ static inline bool arch_pte_access_permitted(u64 pte,
>> bool write, bool execute)
>> }
>> #endif /* CONFIG_PPC_MEM_KEYS */
>>
>> -static inline bool pte_user(pte_t pte)
>> -{
>> -return !(pte_raw(pte) & cpu_to_be64(_PAGE_PRIVILEGED));
>> -}
>> -
>> #define pte_access_permitted pte_access_permitted
>> static inline bool pte_access_permitted(pte_t pte, bool write)
>> {
>> -/*
>> - * _PAGE_READ is needed for any access and will be
>> - * cleared for PROT_NONE
>> - */
>> -if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte))
>> +
>> +if (!pte_present(pte))
>> +return false;
>> +
>> +if (!(pte_read(pte) || pte_exec(pte)))
>> return false;
>>
>> if (write && !pte_write(pte))
>> diff --git a/arch/powerpc/mm/book3s64/hash_utils.c
>> b/arch/powerpc/mm/book3s64/hash_utils.c
>> index ad2afa08e62e..b2eda22195f0 100644
>> --- a/arch/powerpc/mm/book3s64/hash_utils.c
>> +++ b/arch/powerpc/mm/book3s64/hash_utils.c
>> @@ -310,9 +310,26 @@ unsigned long htab_convert_pte_flags(unsigned long
>> pteflags, unsigned long flags
>> else
>>
Re: [RFC PATCH] powerpc/book3s/hash: Drop _PAGE_PRIVILEGED from PAGE_NONE
On Thu Nov 2, 2023 at 11:23 PM AEST, Aneesh Kumar K.V wrote:
> There used to be a dependency on _PAGE_PRIVILEGED with pte_savedwrite.
> But that got dropped by
> commit 6a56ccbcf6c6 ("mm/autonuma: use can_change_(pte|pmd)_writable() to
> replace savedwrite")
>
> With this change numa fault pte (pte_protnone()) gets mapped as regular user
> pte
> with RWX cleared (no-access).
You mean "that" above change (not *this* change), right?
> This also remove pte_user() from
> book3s/64.
Nice cleanup. That was an annoying hack.
> pte_access_permitted() now checks for _PAGE_EXEC because we now support
> EXECONLY mappings.
AFAIKS pte_exec() is not required, GUP is really only for read or
write access. It should be a separate patch if you think it's needed.
>
> Signed-off-by: Aneesh Kumar K.V
> ---
> arch/powerpc/include/asm/book3s/64/pgtable.h | 23 +---
> arch/powerpc/mm/book3s64/hash_utils.c| 17 +++
> 2 files changed, 23 insertions(+), 17 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h
> b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index cb77eddca54b..7c7de7b56df0 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -17,12 +17,6 @@
> #define _PAGE_EXEC 0x1 /* execute permission */
> #define _PAGE_WRITE 0x2 /* write access allowed */
> #define _PAGE_READ 0x4 /* read access allowed */
> -#define _PAGE_NA _PAGE_PRIVILEGED
> -#define _PAGE_NAX_PAGE_EXEC
> -#define _PAGE_RO _PAGE_READ
> -#define _PAGE_ROX(_PAGE_READ | _PAGE_EXEC)
> -#define _PAGE_RW (_PAGE_READ | _PAGE_WRITE)
> -#define _PAGE_RWX(_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC)
> #define _PAGE_PRIVILEGED 0x8 /* kernel access only */
> #define _PAGE_SAO0x00010 /* Strong access order */
> #define _PAGE_NON_IDEMPOTENT 0x00020 /* non idempotent memory */
Did you leave PAGE_NONE as _PAGE_BASE | _PAGE_PRIVILEGED below?
Shouldn't that be changed too? Then this patch is not only hash
but also radix.
Why is the hash change required? Previously PAGE_NONE relied on
privileged bit to prevent access, now you need to handle a PTE
without that bit? In that case could that be patch 1, then the
rest patch 2?
__pte_flags_need_flush() should be updated after this too,
basically revert commit 1abce0580b894.
> @@ -119,9 +113,9 @@
> /*
> * user access blocked by key
> */
> -#define _PAGE_KERNEL_RW (_PAGE_PRIVILEGED | _PAGE_RW |
> _PAGE_DIRTY)
> #define _PAGE_KERNEL_RO (_PAGE_PRIVILEGED | _PAGE_READ)
> #define _PAGE_KERNEL_ROX (_PAGE_PRIVILEGED | _PAGE_READ | _PAGE_EXEC)
> +#define _PAGE_KERNEL_RW (_PAGE_PRIVILEGED | _PAGE_RW |
> _PAGE_DIRTY)
> #define _PAGE_KERNEL_RWX (_PAGE_PRIVILEGED | _PAGE_DIRTY | _PAGE_RW |
> _PAGE_EXEC)
> /*
> * _PAGE_CHG_MASK masks of bits that are to be preserved across
No need to reorder defines.
Thanks,
Nick
> @@ -523,19 +517,14 @@ static inline bool arch_pte_access_permitted(u64 pte,
> bool write, bool execute)
> }
> #endif /* CONFIG_PPC_MEM_KEYS */
>
> -static inline bool pte_user(pte_t pte)
> -{
> - return !(pte_raw(pte) & cpu_to_be64(_PAGE_PRIVILEGED));
> -}
> -
> #define pte_access_permitted pte_access_permitted
> static inline bool pte_access_permitted(pte_t pte, bool write)
> {
> - /*
> - * _PAGE_READ is needed for any access and will be
> - * cleared for PROT_NONE
> - */
> - if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte))
> +
> + if (!pte_present(pte))
> + return false;
> +
> + if (!(pte_read(pte) || pte_exec(pte)))
> return false;
>
> if (write && !pte_write(pte))
> diff --git a/arch/powerpc/mm/book3s64/hash_utils.c
> b/arch/powerpc/mm/book3s64/hash_utils.c
> index ad2afa08e62e..b2eda22195f0 100644
> --- a/arch/powerpc/mm/book3s64/hash_utils.c
> +++ b/arch/powerpc/mm/book3s64/hash_utils.c
> @@ -310,9 +310,26 @@ unsigned long htab_convert_pte_flags(unsigned long
> pteflags, unsigned long flags
> else
> rflags |= 0x3;
> }
> + WARN_ON(!(pteflags & _PAGE_RWX));
> } else {
> if (pteflags & _PAGE_RWX)
> rflags |= 0x2;
> + else {
> + /*
> + * PAGE_NONE will get mapped to 0b110 (slb key 1 no
> access)
> + * We picked 0b110 instead of 0b000 so that slb key 0
> will
> + * get only read only access for the same rflags.
> + */
> + if (mmu_has_feature(MMU_FTR_KERNEL_RO))
> + rflags |= (HPTE_R_PP0 | 0x2);
> + /*
> + * rflags = HPTE_R_N
> + * Without KERNEL_RO feature this will result in
[RFC PATCH] powerpc/book3s/hash: Drop _PAGE_PRIVILEGED from PAGE_NONE
There used to be a dependency on _PAGE_PRIVILEGED with pte_savedwrite.
But that got dropped by
commit 6a56ccbcf6c6 ("mm/autonuma: use can_change_(pte|pmd)_writable() to
replace savedwrite")
With this change numa fault pte (pte_protnone()) gets mapped as regular user pte
with RWX cleared (no-access). This also remove pte_user() from
book3s/64.
pte_access_permitted() now checks for _PAGE_EXEC because we now support
EXECONLY mappings.
Signed-off-by: Aneesh Kumar K.V
---
arch/powerpc/include/asm/book3s/64/pgtable.h | 23 +---
arch/powerpc/mm/book3s64/hash_utils.c| 17 +++
2 files changed, 23 insertions(+), 17 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h
b/arch/powerpc/include/asm/book3s/64/pgtable.h
index cb77eddca54b..7c7de7b56df0 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -17,12 +17,6 @@
#define _PAGE_EXEC 0x1 /* execute permission */
#define _PAGE_WRITE0x2 /* write access allowed */
#define _PAGE_READ 0x4 /* read access allowed */
-#define _PAGE_NA _PAGE_PRIVILEGED
-#define _PAGE_NAX _PAGE_EXEC
-#define _PAGE_RO _PAGE_READ
-#define _PAGE_ROX (_PAGE_READ | _PAGE_EXEC)
-#define _PAGE_RW (_PAGE_READ | _PAGE_WRITE)
-#define _PAGE_RWX (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC)
#define _PAGE_PRIVILEGED 0x8 /* kernel access only */
#define _PAGE_SAO 0x00010 /* Strong access order */
#define _PAGE_NON_IDEMPOTENT 0x00020 /* non idempotent memory */
@@ -119,9 +113,9 @@
/*
* user access blocked by key
*/
-#define _PAGE_KERNEL_RW(_PAGE_PRIVILEGED | _PAGE_RW |
_PAGE_DIRTY)
#define _PAGE_KERNEL_RO (_PAGE_PRIVILEGED | _PAGE_READ)
#define _PAGE_KERNEL_ROX(_PAGE_PRIVILEGED | _PAGE_READ | _PAGE_EXEC)
+#define _PAGE_KERNEL_RW(_PAGE_PRIVILEGED | _PAGE_RW |
_PAGE_DIRTY)
#define _PAGE_KERNEL_RWX (_PAGE_PRIVILEGED | _PAGE_DIRTY | _PAGE_RW |
_PAGE_EXEC)
/*
* _PAGE_CHG_MASK masks of bits that are to be preserved across
@@ -523,19 +517,14 @@ static inline bool arch_pte_access_permitted(u64 pte,
bool write, bool execute)
}
#endif /* CONFIG_PPC_MEM_KEYS */
-static inline bool pte_user(pte_t pte)
-{
- return !(pte_raw(pte) & cpu_to_be64(_PAGE_PRIVILEGED));
-}
-
#define pte_access_permitted pte_access_permitted
static inline bool pte_access_permitted(pte_t pte, bool write)
{
- /*
-* _PAGE_READ is needed for any access and will be
-* cleared for PROT_NONE
-*/
- if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte))
+
+ if (!pte_present(pte))
+ return false;
+
+ if (!(pte_read(pte) || pte_exec(pte)))
return false;
if (write && !pte_write(pte))
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c
b/arch/powerpc/mm/book3s64/hash_utils.c
index ad2afa08e62e..b2eda22195f0 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -310,9 +310,26 @@ unsigned long htab_convert_pte_flags(unsigned long
pteflags, unsigned long flags
else
rflags |= 0x3;
}
+ WARN_ON(!(pteflags & _PAGE_RWX));
} else {
if (pteflags & _PAGE_RWX)
rflags |= 0x2;
+ else {
+ /*
+* PAGE_NONE will get mapped to 0b110 (slb key 1 no
access)
+* We picked 0b110 instead of 0b000 so that slb key 0
will
+* get only read only access for the same rflags.
+*/
+ if (mmu_has_feature(MMU_FTR_KERNEL_RO))
+ rflags |= (HPTE_R_PP0 | 0x2);
+ /*
+* rflags = HPTE_R_N
+* Without KERNEL_RO feature this will result in slb
+* key 0 with read/write. But ISA only supports that.
+* There is no key 1 no-access and key 0 read-only
+* pp bit support.
+*/
+ }
if (!((pteflags & _PAGE_WRITE) && (pteflags & _PAGE_DIRTY)))
rflags |= 0x1;
}
--
2.41.0
