diff mbox series

[mm-unstable,v1,11/26] microblaze/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

Message ID 20230113171026.582290-12-david@redhat.com (mailing list archive)
State New, archived
Headers show
Series [mm-unstable,v1,01/26] mm/debug_vm_pgtable: more pte_swp_exclusive() sanity checks | expand

Commit Message

David Hildenbrand Jan. 13, 2023, 5:10 p.m. UTC
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit
from the type. Generic MM currently only uses 5 bits for the type
(MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused.

The shift by 2 when converting between PTE and arch-specific swap entry
makes the swap PTE layout a little bit harder to decipher.

While at it, drop the comment from paulus---copy-and-paste leftover
from powerpc where we actually have _PAGE_HASHPTE---and mask the type in
__swp_entry_to_pte() as well.

Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 arch/m68k/include/asm/mcf_pgtable.h   |  4 +--
 arch/microblaze/include/asm/pgtable.h | 45 +++++++++++++++++++++------
 2 files changed, 37 insertions(+), 12 deletions(-)

Comments

Geert Uytterhoeven Feb. 26, 2023, 8:13 p.m. UTC | #1
Hi David,

On Fri, Jan 13, 2023 at 6:16 PM David Hildenbrand <david@redhat.com> wrote:
> Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit
> from the type. Generic MM currently only uses 5 bits for the type
> (MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused.
>
> The shift by 2 when converting between PTE and arch-specific swap entry
> makes the swap PTE layout a little bit harder to decipher.
>
> While at it, drop the comment from paulus---copy-and-paste leftover
> from powerpc where we actually have _PAGE_HASHPTE---and mask the type in
> __swp_entry_to_pte() as well.
>
> Cc: Michal Simek <monstr@monstr.eu>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Thanks for your patch, which is now commit b5c88f21531c3457
("microblaze/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE") in

>  arch/m68k/include/asm/mcf_pgtable.h   |  4 +--

What is this m68k change doing here?
Sorry for not noticing this earlier.

Furthermore, several things below look strange to me...

>  arch/microblaze/include/asm/pgtable.h | 45 +++++++++++++++++++++------
>  2 files changed, 37 insertions(+), 12 deletions(-)
>
> diff --git a/arch/m68k/include/asm/mcf_pgtable.h b/arch/m68k/include/asm/mcf_pgtable.h
> index 3f8f4d0e66dd..e573d7b649f7 100644
> --- a/arch/m68k/include/asm/mcf_pgtable.h
> +++ b/arch/m68k/include/asm/mcf_pgtable.h
> @@ -46,8 +46,8 @@
>  #define _CACHEMASK040          (~0x060)
>  #define _PAGE_GLOBAL040                0x400   /* 68040 global bit, used for kva descs */
>
> -/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
> -#define _PAGE_SWP_EXCLUSIVE    0x080
> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
> +#define _PAGE_SWP_EXCLUSIVE    CF_PAGE_NOCACHE

CF_PAGE_NOCACHE is 0x80, so this is still bit 7, thus the new comment
is wrong?

>
>  /*
>   * Externally used page protection values.
> diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
> index 42f5988e998b..7e3de54bf426 100644
> --- a/arch/microblaze/include/asm/pgtable.h
> +++ b/arch/microblaze/include/asm/pgtable.h
> @@ -131,10 +131,10 @@ extern pte_t *va_to_pte(unsigned long address);
>   * of the 16 available.  Bit 24-26 of the TLB are cleared in the TLB
>   * miss handler.  Bit 27 is PAGE_USER, thus selecting the correct
>   * zone.
> - * - PRESENT *must* be in the bottom two bits because swap cache
> - * entries use the top 30 bits.  Because 4xx doesn't support SMP
> - * anyway, M is irrelevant so we borrow it for PAGE_PRESENT.  Bit 30
> - * is cleared in the TLB miss handler before the TLB entry is loaded.
> + * - PRESENT *must* be in the bottom two bits because swap PTEs use the top
> + * 30 bits.  Because 4xx doesn't support SMP anyway, M is irrelevant so we
> + * borrow it for PAGE_PRESENT.  Bit 30 is cleared in the TLB miss handler
> + * before the TLB entry is loaded.

So the PowerPC 4xx comment is still here?

>   * - All other bits of the PTE are loaded into TLBLO without
>   *  * modification, leaving us only the bits 20, 21, 24, 25, 26, 30 for
>   * software PTE bits.  We actually use bits 21, 24, 25, and
> @@ -155,6 +155,9 @@ extern pte_t *va_to_pte(unsigned long address);
>  #define _PAGE_ACCESSED 0x400   /* software: R: page referenced */
>  #define _PMD_PRESENT   PAGE_MASK
>
> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
> +#define _PAGE_SWP_EXCLUSIVE    _PAGE_DIRTY

_PAGE_DIRTY is 0x80, so this is also bit 7, thus the new comment is
wrong?

Gr{oetje,eeting}s,

                        Geert
David Hildenbrand Feb. 27, 2023, 1:31 p.m. UTC | #2
On 26.02.23 21:13, Geert Uytterhoeven wrote:
> Hi David,

Hi Geert,

> 
> On Fri, Jan 13, 2023 at 6:16 PM David Hildenbrand <david@redhat.com> wrote:
>> Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit
>> from the type. Generic MM currently only uses 5 bits for the type
>> (MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused.
>>
>> The shift by 2 when converting between PTE and arch-specific swap entry
>> makes the swap PTE layout a little bit harder to decipher.
>>
>> While at it, drop the comment from paulus---copy-and-paste leftover
>> from powerpc where we actually have _PAGE_HASHPTE---and mask the type in
>> __swp_entry_to_pte() as well.
>>
>> Cc: Michal Simek <monstr@monstr.eu>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> Thanks for your patch, which is now commit b5c88f21531c3457
> ("microblaze/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE") in
> 

Right, it went upstream, so we can only fixup.

>>   arch/m68k/include/asm/mcf_pgtable.h   |  4 +--
> 
> What is this m68k change doing here?
> Sorry for not noticing this earlier.

Thanks for the late review, still valuable :)

That hunk should have gone into the previous patch, looks like I messed 
that up when reworking.

> 
> Furthermore, several things below look strange to me...
> 
>>   arch/microblaze/include/asm/pgtable.h | 45 +++++++++++++++++++++------
>>   2 files changed, 37 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/m68k/include/asm/mcf_pgtable.h b/arch/m68k/include/asm/mcf_pgtable.h
>> index 3f8f4d0e66dd..e573d7b649f7 100644
>> --- a/arch/m68k/include/asm/mcf_pgtable.h
>> +++ b/arch/m68k/include/asm/mcf_pgtable.h
>> @@ -46,8 +46,8 @@
>>   #define _CACHEMASK040          (~0x060)
>>   #define _PAGE_GLOBAL040                0x400   /* 68040 global bit, used for kva descs */
>>
>> -/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
>> -#define _PAGE_SWP_EXCLUSIVE    0x080
>> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
>> +#define _PAGE_SWP_EXCLUSIVE    CF_PAGE_NOCACHE
> 
> CF_PAGE_NOCACHE is 0x80, so this is still bit 7, thus the new comment
> is wrong?

You're right, it's still bit 7 (and we use LSB-0 bit numbering in that 
file). I'll send a fixup.

> 
>>
>>   /*
>>    * Externally used page protection values.
>> diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
>> index 42f5988e998b..7e3de54bf426 100644
>> --- a/arch/microblaze/include/asm/pgtable.h
>> +++ b/arch/microblaze/include/asm/pgtable.h
>> @@ -131,10 +131,10 @@ extern pte_t *va_to_pte(unsigned long address);
>>    * of the 16 available.  Bit 24-26 of the TLB are cleared in the TLB
>>    * miss handler.  Bit 27 is PAGE_USER, thus selecting the correct
>>    * zone.
>> - * - PRESENT *must* be in the bottom two bits because swap cache
>> - * entries use the top 30 bits.  Because 4xx doesn't support SMP
>> - * anyway, M is irrelevant so we borrow it for PAGE_PRESENT.  Bit 30
>> - * is cleared in the TLB miss handler before the TLB entry is loaded.
>> + * - PRESENT *must* be in the bottom two bits because swap PTEs use the top
>> + * 30 bits.  Because 4xx doesn't support SMP anyway, M is irrelevant so we
>> + * borrow it for PAGE_PRESENT.  Bit 30 is cleared in the TLB miss handler
>> + * before the TLB entry is loaded.
> 
> So the PowerPC 4xx comment is still here?

I only dropped the comment above __swp_type(). I guess you mean that we 
could also drop the "Because 4xx doesn't support SMP anyway, M is 
irrelevant so we borrow it for PAGE_PRESENT." sentence, correct? Not 
sure about the "Bit 30 is cleared in the TLB miss handler" comment, if 
that can similarly be dropped.

> 
>>    * - All other bits of the PTE are loaded into TLBLO without
>>    *  * modification, leaving us only the bits 20, 21, 24, 25, 26, 30 for
>>    * software PTE bits.  We actually use bits 21, 24, 25, and
>> @@ -155,6 +155,9 @@ extern pte_t *va_to_pte(unsigned long address);
>>   #define _PAGE_ACCESSED 0x400   /* software: R: page referenced */
>>   #define _PMD_PRESENT   PAGE_MASK
>>
>> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
>> +#define _PAGE_SWP_EXCLUSIVE    _PAGE_DIRTY
> 
> _PAGE_DIRTY is 0x80, so this is also bit 7, thus the new comment is
> wrong?

In the example, I use MSB-0 bit numbering (which I determined to be 
correct in microblaze context eventually, but I got confused a couple a 
times because it's very inconsistent). That should be MSB-0 bit 24.

Thanks!
Geert Uytterhoeven Feb. 27, 2023, 2:43 p.m. UTC | #3
Hi David,

On Mon, Feb 27, 2023 at 2:31 PM David Hildenbrand <david@redhat.com> wrote:
> On 26.02.23 21:13, Geert Uytterhoeven wrote:
> > On Fri, Jan 13, 2023 at 6:16 PM David Hildenbrand <david@redhat.com> wrote:
> >> Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit
> >> from the type. Generic MM currently only uses 5 bits for the type
> >> (MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused.
> >>
> >> The shift by 2 when converting between PTE and arch-specific swap entry
> >> makes the swap PTE layout a little bit harder to decipher.
> >>
> >> While at it, drop the comment from paulus---copy-and-paste leftover
> >> from powerpc where we actually have _PAGE_HASHPTE---and mask the type in
> >> __swp_entry_to_pte() as well.
> >>
> >> Cc: Michal Simek <monstr@monstr.eu>
> >> Signed-off-by: David Hildenbrand <david@redhat.com>
> >
> > Thanks for your patch, which is now commit b5c88f21531c3457
> > ("microblaze/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE") in
> >
>
> Right, it went upstream, so we can only fixup.
>
> >>   arch/m68k/include/asm/mcf_pgtable.h   |  4 +--
> >
> > What is this m68k change doing here?
> > Sorry for not noticing this earlier.
>
> Thanks for the late review, still valuable :)
>
> That hunk should have gone into the previous patch, looks like I messed
> that up when reworking.
>
> >
> > Furthermore, several things below look strange to me...
> >
> >>   arch/microblaze/include/asm/pgtable.h | 45 +++++++++++++++++++++------
> >>   2 files changed, 37 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/arch/m68k/include/asm/mcf_pgtable.h b/arch/m68k/include/asm/mcf_pgtable.h
> >> index 3f8f4d0e66dd..e573d7b649f7 100644
> >> --- a/arch/m68k/include/asm/mcf_pgtable.h
> >> +++ b/arch/m68k/include/asm/mcf_pgtable.h
> >> @@ -46,8 +46,8 @@
> >>   #define _CACHEMASK040          (~0x060)
> >>   #define _PAGE_GLOBAL040                0x400   /* 68040 global bit, used for kva descs */
> >>
> >> -/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
> >> -#define _PAGE_SWP_EXCLUSIVE    0x080
> >> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
> >> +#define _PAGE_SWP_EXCLUSIVE    CF_PAGE_NOCACHE
> >
> > CF_PAGE_NOCACHE is 0x80, so this is still bit 7, thus the new comment
> > is wrong?
>
> You're right, it's still bit 7 (and we use LSB-0 bit numbering in that
> file). I'll send a fixup.

OK.

> >>   /*
> >>    * Externally used page protection values.
> >> diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
> >> index 42f5988e998b..7e3de54bf426 100644
> >> --- a/arch/microblaze/include/asm/pgtable.h
> >> +++ b/arch/microblaze/include/asm/pgtable.h
> >> @@ -131,10 +131,10 @@ extern pte_t *va_to_pte(unsigned long address);
> >>    * of the 16 available.  Bit 24-26 of the TLB are cleared in the TLB
> >>    * miss handler.  Bit 27 is PAGE_USER, thus selecting the correct
> >>    * zone.
> >> - * - PRESENT *must* be in the bottom two bits because swap cache
> >> - * entries use the top 30 bits.  Because 4xx doesn't support SMP
> >> - * anyway, M is irrelevant so we borrow it for PAGE_PRESENT.  Bit 30
> >> - * is cleared in the TLB miss handler before the TLB entry is loaded.
> >> + * - PRESENT *must* be in the bottom two bits because swap PTEs use the top
> >> + * 30 bits.  Because 4xx doesn't support SMP anyway, M is irrelevant so we
> >> + * borrow it for PAGE_PRESENT.  Bit 30 is cleared in the TLB miss handler
> >> + * before the TLB entry is loaded.
> >
> > So the PowerPC 4xx comment is still here?
>
> I only dropped the comment above __swp_type(). I guess you mean that we
> could also drop the "Because 4xx doesn't support SMP anyway, M is
> irrelevant so we borrow it for PAGE_PRESENT." sentence, correct? Not

Yes, that's what I meant.

> sure about the "Bit 30 is cleared in the TLB miss handler" comment, if
> that can similarly be dropped.

No idea, didn't check. But if it was copied from PPC, chances are
high it's no longer true....

> >>    * - All other bits of the PTE are loaded into TLBLO without
> >>    *  * modification, leaving us only the bits 20, 21, 24, 25, 26, 30 for
> >>    * software PTE bits.  We actually use bits 21, 24, 25, and
> >> @@ -155,6 +155,9 @@ extern pte_t *va_to_pte(unsigned long address);
> >>   #define _PAGE_ACCESSED 0x400   /* software: R: page referenced */
> >>   #define _PMD_PRESENT   PAGE_MASK
> >>
> >> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
> >> +#define _PAGE_SWP_EXCLUSIVE    _PAGE_DIRTY
> >
> > _PAGE_DIRTY is 0x80, so this is also bit 7, thus the new comment is
> > wrong?
>
> In the example, I use MSB-0 bit numbering (which I determined to be
> correct in microblaze context eventually, but I got confused a couple a
> times because it's very inconsistent). That should be MSB-0 bit 24.

Thanks, TIL microblaze uses IBM bit numbering...

Gr{oetje,eeting}s,

                        Geert
David Hildenbrand Feb. 27, 2023, 5:01 p.m. UTC | #4
>>>>    /*
>>>>     * Externally used page protection values.
>>>> diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
>>>> index 42f5988e998b..7e3de54bf426 100644
>>>> --- a/arch/microblaze/include/asm/pgtable.h
>>>> +++ b/arch/microblaze/include/asm/pgtable.h
>>>> @@ -131,10 +131,10 @@ extern pte_t *va_to_pte(unsigned long address);
>>>>     * of the 16 available.  Bit 24-26 of the TLB are cleared in the TLB
>>>>     * miss handler.  Bit 27 is PAGE_USER, thus selecting the correct
>>>>     * zone.
>>>> - * - PRESENT *must* be in the bottom two bits because swap cache
>>>> - * entries use the top 30 bits.  Because 4xx doesn't support SMP
>>>> - * anyway, M is irrelevant so we borrow it for PAGE_PRESENT.  Bit 30
>>>> - * is cleared in the TLB miss handler before the TLB entry is loaded.
>>>> + * - PRESENT *must* be in the bottom two bits because swap PTEs use the top
>>>> + * 30 bits.  Because 4xx doesn't support SMP anyway, M is irrelevant so we
>>>> + * borrow it for PAGE_PRESENT.  Bit 30 is cleared in the TLB miss handler
>>>> + * before the TLB entry is loaded.
>>>
>>> So the PowerPC 4xx comment is still here?
>>
>> I only dropped the comment above __swp_type(). I guess you mean that we
>> could also drop the "Because 4xx doesn't support SMP anyway, M is
>> irrelevant so we borrow it for PAGE_PRESENT." sentence, correct? Not
> 
> Yes, that's what I meant.
> 
>> sure about the "Bit 30 is cleared in the TLB miss handler" comment, if
>> that can similarly be dropped.
> 
> No idea, didn't check. But if it was copied from PPC, chances are
> high it's no longer true....

I'll have a look.

> 
>>>>     * - All other bits of the PTE are loaded into TLBLO without
>>>>     *  * modification, leaving us only the bits 20, 21, 24, 25, 26, 30 for
>>>>     * software PTE bits.  We actually use bits 21, 24, 25, and
>>>> @@ -155,6 +155,9 @@ extern pte_t *va_to_pte(unsigned long address);
>>>>    #define _PAGE_ACCESSED 0x400   /* software: R: page referenced */
>>>>    #define _PMD_PRESENT   PAGE_MASK
>>>>
>>>> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
>>>> +#define _PAGE_SWP_EXCLUSIVE    _PAGE_DIRTY
>>>
>>> _PAGE_DIRTY is 0x80, so this is also bit 7, thus the new comment is
>>> wrong?
>>
>> In the example, I use MSB-0 bit numbering (which I determined to be
>> correct in microblaze context eventually, but I got confused a couple a
>> times because it's very inconsistent). That should be MSB-0 bit 24.
> 
> Thanks, TIL microblaze uses IBM bit numbering...

I assume IBM bit numbering corresponds to MSB-0 bit numbering, correct?


I recall that I used the comment above "/* Definitions for MicroBlaze. 
*/" as an orientation.

0  1  2  3  4  ... 18 19 20 21 22 23 24 25 26 27 28 29 30 31
RPN.....................  0  0 EX WR ZSEL.......  W  I  M  G


So ... either we adjust both or we leave it as is. (again, depends on 
what the right thing to to is -- which I don't know :) )
Geert Uytterhoeven Feb. 27, 2023, 7:46 p.m. UTC | #5
Hi David,

On Mon, Feb 27, 2023 at 6:01 PM David Hildenbrand <david@redhat.com> wrote:
> >>>>    /*
> >>>>     * Externally used page protection values.
> >>>> diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
> >>>> index 42f5988e998b..7e3de54bf426 100644
> >>>> --- a/arch/microblaze/include/asm/pgtable.h
> >>>> +++ b/arch/microblaze/include/asm/pgtable.h

> >>>>     * - All other bits of the PTE are loaded into TLBLO without
> >>>>     *  * modification, leaving us only the bits 20, 21, 24, 25, 26, 30 for
> >>>>     * software PTE bits.  We actually use bits 21, 24, 25, and
> >>>> @@ -155,6 +155,9 @@ extern pte_t *va_to_pte(unsigned long address);
> >>>>    #define _PAGE_ACCESSED 0x400   /* software: R: page referenced */
> >>>>    #define _PMD_PRESENT   PAGE_MASK
> >>>>
> >>>> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
> >>>> +#define _PAGE_SWP_EXCLUSIVE    _PAGE_DIRTY
> >>>
> >>> _PAGE_DIRTY is 0x80, so this is also bit 7, thus the new comment is
> >>> wrong?
> >>
> >> In the example, I use MSB-0 bit numbering (which I determined to be
> >> correct in microblaze context eventually, but I got confused a couple a
> >> times because it's very inconsistent). That should be MSB-0 bit 24.
> >
> > Thanks, TIL microblaze uses IBM bit numbering...
>
> I assume IBM bit numbering corresponds to MSB-0 bit numbering, correct?

Correct, as seen in s370 and PowerPC manuals...

> I recall that I used the comment above "/* Definitions for MicroBlaze.
> */" as an orientation.
>
> 0  1  2  3  4  ... 18 19 20 21 22 23 24 25 26 27 28 29 30 31
> RPN.....................  0  0 EX WR ZSEL.......  W  I  M  G

Indeed, that's where I noticed the "unconventional" numbering...

> So ... either we adjust both or we leave it as is. (again, depends on
> what the right thing to to is -- which I don't know :) )

It depends whether you want to match the hardware documentation,
or the Linux BIT() macro and friends...

Gr{oetje,eeting}s,

                        Geert
David Hildenbrand Feb. 28, 2023, 3:55 p.m. UTC | #6
On 27.02.23 20:46, Geert Uytterhoeven wrote:
> Hi David,
> 
> On Mon, Feb 27, 2023 at 6:01 PM David Hildenbrand <david@redhat.com> wrote:
>>>>>>     /*
>>>>>>      * Externally used page protection values.
>>>>>> diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
>>>>>> index 42f5988e998b..7e3de54bf426 100644
>>>>>> --- a/arch/microblaze/include/asm/pgtable.h
>>>>>> +++ b/arch/microblaze/include/asm/pgtable.h
> 
>>>>>>      * - All other bits of the PTE are loaded into TLBLO without
>>>>>>      *  * modification, leaving us only the bits 20, 21, 24, 25, 26, 30 for
>>>>>>      * software PTE bits.  We actually use bits 21, 24, 25, and
>>>>>> @@ -155,6 +155,9 @@ extern pte_t *va_to_pte(unsigned long address);
>>>>>>     #define _PAGE_ACCESSED 0x400   /* software: R: page referenced */
>>>>>>     #define _PMD_PRESENT   PAGE_MASK
>>>>>>
>>>>>> +/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
>>>>>> +#define _PAGE_SWP_EXCLUSIVE    _PAGE_DIRTY
>>>>>
>>>>> _PAGE_DIRTY is 0x80, so this is also bit 7, thus the new comment is
>>>>> wrong?
>>>>
>>>> In the example, I use MSB-0 bit numbering (which I determined to be
>>>> correct in microblaze context eventually, but I got confused a couple a
>>>> times because it's very inconsistent). That should be MSB-0 bit 24.
>>>
>>> Thanks, TIL microblaze uses IBM bit numbering...
>>
>> I assume IBM bit numbering corresponds to MSB-0 bit numbering, correct?
> 
> Correct, as seen in s370 and PowerPC manuals...

Good, I have some solid s390x background, but thinking about the term 
"IBM PC" made me double-check that we're talking about the same thing ;)

> 
>> I recall that I used the comment above "/* Definitions for MicroBlaze.
>> */" as an orientation.
>>
>> 0  1  2  3  4  ... 18 19 20 21 22 23 24 25 26 27 28 29 30 31
>> RPN.....................  0  0 EX WR ZSEL.......  W  I  M  G
> 
> Indeed, that's where I noticed the "unconventional" numbering...
> 
>> So ... either we adjust both or we leave it as is. (again, depends on
>> what the right thing to to is -- which I don't know :) )
> 
> It depends whether you want to match the hardware documentation,
> or the Linux BIT() macro and friends...

The hardware documentation, so we should be good.

Thanks!
diff mbox series

Patch

diff --git a/arch/m68k/include/asm/mcf_pgtable.h b/arch/m68k/include/asm/mcf_pgtable.h
index 3f8f4d0e66dd..e573d7b649f7 100644
--- a/arch/m68k/include/asm/mcf_pgtable.h
+++ b/arch/m68k/include/asm/mcf_pgtable.h
@@ -46,8 +46,8 @@ 
 #define _CACHEMASK040		(~0x060)
 #define _PAGE_GLOBAL040		0x400   /* 68040 global bit, used for kva descs */
 
-/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
-#define _PAGE_SWP_EXCLUSIVE	0x080
+/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE	CF_PAGE_NOCACHE
 
 /*
  * Externally used page protection values.
diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
index 42f5988e998b..7e3de54bf426 100644
--- a/arch/microblaze/include/asm/pgtable.h
+++ b/arch/microblaze/include/asm/pgtable.h
@@ -131,10 +131,10 @@  extern pte_t *va_to_pte(unsigned long address);
  * of the 16 available.  Bit 24-26 of the TLB are cleared in the TLB
  * miss handler.  Bit 27 is PAGE_USER, thus selecting the correct
  * zone.
- * - PRESENT *must* be in the bottom two bits because swap cache
- * entries use the top 30 bits.  Because 4xx doesn't support SMP
- * anyway, M is irrelevant so we borrow it for PAGE_PRESENT.  Bit 30
- * is cleared in the TLB miss handler before the TLB entry is loaded.
+ * - PRESENT *must* be in the bottom two bits because swap PTEs use the top
+ * 30 bits.  Because 4xx doesn't support SMP anyway, M is irrelevant so we
+ * borrow it for PAGE_PRESENT.  Bit 30 is cleared in the TLB miss handler
+ * before the TLB entry is loaded.
  * - All other bits of the PTE are loaded into TLBLO without
  *  * modification, leaving us only the bits 20, 21, 24, 25, 26, 30 for
  * software PTE bits.  We actually use bits 21, 24, 25, and
@@ -155,6 +155,9 @@  extern pte_t *va_to_pte(unsigned long address);
 #define _PAGE_ACCESSED	0x400	/* software: R: page referenced */
 #define _PMD_PRESENT	PAGE_MASK
 
+/* We borrow bit 24 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE	_PAGE_DIRTY
+
 /*
  * Some bits are unused...
  */
@@ -393,18 +396,40 @@  static inline unsigned long pmd_page_vaddr(pmd_t pmd)
 extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
 
 /*
- * Encode and decode a swap entry.
- * Note that the bits we use in a PTE for representing a swap entry
- * must not include the _PAGE_PRESENT bit, or the _PAGE_HASHPTE bit
- * (if used).  -- paulus
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
+ *
+ *                         1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
+ *   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ *   <------------------ offset -------------------> E < type -> 0 0
+ *
+ *   E is the exclusive marker that is not stored in swap entries.
  */
-#define __swp_type(entry)		((entry).val & 0x3f)
+#define __swp_type(entry)	((entry).val & 0x1f)
 #define __swp_offset(entry)	((entry).val >> 6)
 #define __swp_entry(type, offset) \
-		((swp_entry_t) { (type) | ((offset) << 6) })
+		((swp_entry_t) { ((type) & 0x1f) | ((offset) << 6) })
 #define __pte_to_swp_entry(pte)	((swp_entry_t) { pte_val(pte) >> 2 })
 #define __swp_entry_to_pte(x)	((pte_t) { (x).val << 2 })
 
+#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline int pte_swp_exclusive(pte_t pte)
+{
+	return pte_val(pte) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+	pte_val(pte) |= _PAGE_SWP_EXCLUSIVE;
+	return pte;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+	pte_val(pte) &= ~_PAGE_SWP_EXCLUSIVE;
+	return pte;
+}
+
 extern unsigned long iopa(unsigned long addr);
 
 /* Values for nocacheflag and cmode */