* [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW @ 2014-12-22 10:14 ` Christophe Leroy 0 siblings, 0 replies; 10+ messages in thread From: Christophe Leroy @ 2014-12-22 10:14 UTC (permalink / raw) To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman, scottwood Cc: linux-kernel, linuxppc-dev, Joakim Tjernlund On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> --- v2 is a complete rework compared to v1 v3: fixing pte_update() and comments arch/powerpc/include/asm/pgtable-ppc32.h | 5 +++-- arch/powerpc/include/asm/pte-8xx.h | 9 ++++----- arch/powerpc/kernel/head_8xx.S | 3 --- 3 files changed, 7 insertions(+), 10 deletions(-) diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h index caf094a..b4e0c3b 100644 --- a/arch/powerpc/include/asm/pgtable-ppc32.h +++ b/arch/powerpc/include/asm/pgtable-ppc32.h @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, andc %1,%0,%5\n\ or %1,%1,%6\n\ /* 0x200 == Extended encoding, bit 22 */ \ - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \ + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is set */ \ rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ + xori %3,%3,0x200\n \ or %1,%3,%1\n\ xori %1,%1,0x200\n" " stwcx. %1,0,%4\n\ diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h index daa4616..eb6edb4 100644 --- a/arch/powerpc/include/asm/pte-8xx.h +++ b/arch/powerpc/include/asm/pte-8xx.h @@ -46,9 +46,9 @@ * require a TLB exception handler change. It is assumed unused bits * are always zero. */ -#define _PAGE_RW 0x0400 /* lsb PP bits, inverted in HW */ +#define _PAGE_RO 0x0400 /* lsb PP bits */ #define _PAGE_USER 0x0800 /* msb PP bits */ -/* set when neither _PAGE_USER nor _PAGE_RW are set */ +/* set when _PAGE_USER is unset and _PAGE_RO is set */ #define _PAGE_KNLRO 0x0200 #define _PMD_PRESENT 0x0001 @@ -62,9 +62,8 @@ #define PTE_ATOMIC_UPDATES 1 /* We need to add _PAGE_SHARED to kernel pages */ -#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_KNLRO) -#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_KNLRO) -#define _PAGE_KERNEL_RW (_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE) +#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_RO | _PAGE_KNLRO) +#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_RO | _PAGE_KNLRO) #endif /* __KERNEL__ */ #endif /* _ASM_POWERPC_PTE_8xx_H */ diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S index 3d4b8ee..807b0db 100644 --- a/arch/powerpc/kernel/head_8xx.S +++ b/arch/powerpc/kernel/head_8xx.S @@ -441,9 +441,6 @@ DataStoreTLBMiss: and r11, r11, r10 rlwimi r10, r11, 0, _PAGE_PRESENT #endif - /* invert RW */ - xori r10, r10, _PAGE_RW - /* The Linux PTE won't go exactly into the MMU TLB. * Software indicator bits 22 and 28 must be clear. * Software indicator bits 24, 25, 26, and 27 must be -- 2.1.0 ^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW @ 2014-12-22 10:14 ` Christophe Leroy 0 siblings, 0 replies; 10+ messages in thread From: Christophe Leroy @ 2014-12-22 10:14 UTC (permalink / raw) To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman, scottwood Cc: linuxppc-dev, linux-kernel On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> --- v2 is a complete rework compared to v1 v3: fixing pte_update() and comments arch/powerpc/include/asm/pgtable-ppc32.h | 5 +++-- arch/powerpc/include/asm/pte-8xx.h | 9 ++++----- arch/powerpc/kernel/head_8xx.S | 3 --- 3 files changed, 7 insertions(+), 10 deletions(-) diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h index caf094a..b4e0c3b 100644 --- a/arch/powerpc/include/asm/pgtable-ppc32.h +++ b/arch/powerpc/include/asm/pgtable-ppc32.h @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, andc %1,%0,%5\n\ or %1,%1,%6\n\ /* 0x200 == Extended encoding, bit 22 */ \ - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \ + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is set */ \ rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ + xori %3,%3,0x200\n \ or %1,%3,%1\n\ xori %1,%1,0x200\n" " stwcx. %1,0,%4\n\ diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h index daa4616..eb6edb4 100644 --- a/arch/powerpc/include/asm/pte-8xx.h +++ b/arch/powerpc/include/asm/pte-8xx.h @@ -46,9 +46,9 @@ * require a TLB exception handler change. It is assumed unused bits * are always zero. */ -#define _PAGE_RW 0x0400 /* lsb PP bits, inverted in HW */ +#define _PAGE_RO 0x0400 /* lsb PP bits */ #define _PAGE_USER 0x0800 /* msb PP bits */ -/* set when neither _PAGE_USER nor _PAGE_RW are set */ +/* set when _PAGE_USER is unset and _PAGE_RO is set */ #define _PAGE_KNLRO 0x0200 #define _PMD_PRESENT 0x0001 @@ -62,9 +62,8 @@ #define PTE_ATOMIC_UPDATES 1 /* We need to add _PAGE_SHARED to kernel pages */ -#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_KNLRO) -#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_KNLRO) -#define _PAGE_KERNEL_RW (_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE) +#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_RO | _PAGE_KNLRO) +#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_RO | _PAGE_KNLRO) #endif /* __KERNEL__ */ #endif /* _ASM_POWERPC_PTE_8xx_H */ diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S index 3d4b8ee..807b0db 100644 --- a/arch/powerpc/kernel/head_8xx.S +++ b/arch/powerpc/kernel/head_8xx.S @@ -441,9 +441,6 @@ DataStoreTLBMiss: and r11, r11, r10 rlwimi r10, r11, 0, _PAGE_PRESENT #endif - /* invert RW */ - xori r10, r10, _PAGE_RW - /* The Linux PTE won't go exactly into the MMU TLB. * Software indicator bits 22 and 28 must be clear. * Software indicator bits 24, 25, 26, and 27 must be -- 2.1.0 ^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW 2014-12-22 10:14 ` Christophe Leroy @ 2015-01-05 18:12 ` Joakim Tjernlund -1 siblings, 0 replies; 10+ messages in thread From: Joakim Tjernlund @ 2015-01-05 18:12 UTC (permalink / raw) To: christophe.leroy; +Cc: scottwood, paulus, mpe, benh, linux-kernel, linuxppc-dev On Mon, 2014-12-22 at 11:14 +0100, Christophe Leroy wrote: > On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages > and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW > > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Hi Christophe, been meaning to look over all you recent 8xx MMU/TLB patches but got so little time :( This is very cool (not sure if there will be a performance gain) but .. > > > > diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h > index caf094a..b4e0c3b 100644 > --- a/arch/powerpc/include/asm/pgtable-ppc32.h > +++ b/arch/powerpc/include/asm/pgtable-ppc32.h > @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, > andc %1,%0,%5\n\ > or %1,%1,%6\n\ > /* 0x200 == Extended encoding, bit 22 */ \ > - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \ > + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is set */ \ > rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ > - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ > + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ > + xori %3,%3,0x200\n \ > or %1,%3,%1\n\ > xori %1,%1,0x200\n" > " stwcx. %1,0,%4\n\ ... here I expected to loose the existing xori insn instead of adding one? Jocke ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW @ 2015-01-05 18:12 ` Joakim Tjernlund 0 siblings, 0 replies; 10+ messages in thread From: Joakim Tjernlund @ 2015-01-05 18:12 UTC (permalink / raw) To: christophe.leroy; +Cc: linux-kernel, paulus, scottwood, linuxppc-dev On Mon, 2014-12-22 at 11:14 +0100, Christophe Leroy wrote: > On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages > and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_= RW >=20 > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Hi Christophe, been meaning to look over all you recent 8xx MMU/TLB patches but got so little time :( This is very cool (not sure if there will be a performance gain) but .. >=20 >=20 >=20 > diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/incl= ude/asm/pgtable-ppc32.h > index caf094a..b4e0c3b 100644 > --- a/arch/powerpc/include/asm/pgtable-ppc32.h > +++ b/arch/powerpc/include/asm/pgtable-ppc32.h > @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, > andc %1,%0,%5\n\ > or %1,%1,%6\n\ > /* 0x200 =3D=3D Extended encoding, bit 22 */ \ > - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set = */ \ > + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is se= t */ \ > rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ > - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ > + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ > + xori %3,%3,0x200\n \ > or %1,%3,%1\n\ > xori %1,%1,0x200\n" > " stwcx. %1,0,%4\n\ ... here I expected to loose the existing xori insn instead of adding one? Jocke= ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW 2015-01-05 18:12 ` Joakim Tjernlund @ 2015-01-06 7:03 ` leroy christophe -1 siblings, 0 replies; 10+ messages in thread From: leroy christophe @ 2015-01-06 7:03 UTC (permalink / raw) To: Joakim Tjernlund; +Cc: scottwood, paulus, mpe, benh, linux-kernel, linuxppc-dev Le 05/01/2015 19:12, Joakim Tjernlund a écrit : > On Mon, 2014-12-22 at 11:14 +0100, Christophe Leroy wrote: >> On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages >> and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW >> >> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > Hi Christophe, been meaning to look over all you recent 8xx MMU/TLB patches > but got so little time :( > > This is very cool (not sure if there will be a performance gain) but .. I think every saved cycle is worth it. Before I did any modification: * ITLBMiss was 28 instructions. * DTLBMiss was 32 instructions. Now, (No MODULES, no CPU6, no CPU15): * ITLBMiss is 15 instructions * DTLBMiss is 24 instructions >> >> >> diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h >> index caf094a..b4e0c3b 100644 >> --- a/arch/powerpc/include/asm/pgtable-ppc32.h >> +++ b/arch/powerpc/include/asm/pgtable-ppc32.h >> @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, >> andc %1,%0,%5\n\ >> or %1,%1,%6\n\ >> /* 0x200 == Extended encoding, bit 22 */ \ >> - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \ >> + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is set */ \ >> rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ >> - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ >> + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ >> + xori %3,%3,0x200\n \ >> or %1,%3,%1\n\ >> xori %1,%1,0x200\n" >> " stwcx. %1,0,%4\n\ > ... here I expected to loose the existing xori insn instead of adding one? > > Well, I could have xored the PAGE_USER bit instead, but in that case, it is not anymore an 'or' but an 'and' that has to be performed between the bits, and then all other bits must be set to 1, or the result of the 'and' shall be inserted using 'rlwimi'. So it would be more modifications than just adding an xori, and not less instructions. Christophe ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW @ 2015-01-06 7:03 ` leroy christophe 0 siblings, 0 replies; 10+ messages in thread From: leroy christophe @ 2015-01-06 7:03 UTC (permalink / raw) To: Joakim Tjernlund; +Cc: linux-kernel, paulus, scottwood, linuxppc-dev Le 05/01/2015 19:12, Joakim Tjernlund a écrit : > On Mon, 2014-12-22 at 11:14 +0100, Christophe Leroy wrote: >> On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages >> and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW >> >> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > Hi Christophe, been meaning to look over all you recent 8xx MMU/TLB patches > but got so little time :( > > This is very cool (not sure if there will be a performance gain) but .. I think every saved cycle is worth it. Before I did any modification: * ITLBMiss was 28 instructions. * DTLBMiss was 32 instructions. Now, (No MODULES, no CPU6, no CPU15): * ITLBMiss is 15 instructions * DTLBMiss is 24 instructions >> >> >> diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h >> index caf094a..b4e0c3b 100644 >> --- a/arch/powerpc/include/asm/pgtable-ppc32.h >> +++ b/arch/powerpc/include/asm/pgtable-ppc32.h >> @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, >> andc %1,%0,%5\n\ >> or %1,%1,%6\n\ >> /* 0x200 == Extended encoding, bit 22 */ \ >> - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \ >> + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is set */ \ >> rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ >> - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ >> + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ >> + xori %3,%3,0x200\n \ >> or %1,%3,%1\n\ >> xori %1,%1,0x200\n" >> " stwcx. %1,0,%4\n\ > ... here I expected to loose the existing xori insn instead of adding one? > > Well, I could have xored the PAGE_USER bit instead, but in that case, it is not anymore an 'or' but an 'and' that has to be performed between the bits, and then all other bits must be set to 1, or the result of the 'and' shall be inserted using 'rlwimi'. So it would be more modifications than just adding an xori, and not less instructions. Christophe ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW 2015-01-06 7:03 ` leroy christophe @ 2015-01-06 13:05 ` Joakim Tjernlund -1 siblings, 0 replies; 10+ messages in thread From: Joakim Tjernlund @ 2015-01-06 13:05 UTC (permalink / raw) To: christophe.leroy; +Cc: scottwood, paulus, mpe, benh, linux-kernel, linuxppc-dev On Tue, 2015-01-06 at 08:03 +0100, leroy christophe wrote: > Le 05/01/2015 19:12, Joakim Tjernlund a écrit : > > On Mon, 2014-12-22 at 11:14 +0100, Christophe Leroy wrote: > > > On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages > > > and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW > > > > > > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > > Hi Christophe, been meaning to look over all you recent 8xx MMU/TLB patches > > but got so little time :( > > > > This is very cool (not sure if there will be a performance gain) but .. > I think every saved cycle is worth it. > Before I did any modification: > * ITLBMiss was 28 instructions. > * DTLBMiss was 32 instructions. > Now, (No MODULES, no CPU6, no CPU15): > * ITLBMiss is 15 instructions > * DTLBMiss is 24 instructions I only meant this patch, sorry for not being explicit about that. > > > > > > > > > diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h > > > index caf094a..b4e0c3b 100644 > > > --- a/arch/powerpc/include/asm/pgtable-ppc32.h > > > +++ b/arch/powerpc/include/asm/pgtable-ppc32.h > > > @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, > > > andc %1,%0,%5\n\ > > > or %1,%1,%6\n\ > > > /* 0x200 == Extended encoding, bit 22 */ \ > > > - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \ > > > + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is set */ \ > > > rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ > > > - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ > > > + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ > > > + xori %3,%3,0x200\n \ > > > or %1,%3,%1\n\ > > > xori %1,%1,0x200\n" > > > " stwcx. %1,0,%4\n\ > > ... here I expected to loose the existing xori insn instead of adding one? > > > > > Well, I could have xored the PAGE_USER bit instead, but in that case, it > is not anymore an 'or' but an 'and' that has to be performed between the > bits, and then all other bits must be set to 1, or the result of the 'and' shall be inserted using 'rlwimi'. So it would be more modifications than just adding an xori, and not less instructions. > I see, thanks Jocke ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW @ 2015-01-06 13:05 ` Joakim Tjernlund 0 siblings, 0 replies; 10+ messages in thread From: Joakim Tjernlund @ 2015-01-06 13:05 UTC (permalink / raw) To: christophe.leroy; +Cc: linux-kernel, paulus, scottwood, linuxppc-dev On Tue, 2015-01-06 at 08:03 +0100, leroy christophe wrote: > Le 05/01/2015 19:12, Joakim Tjernlund a =E9crit : > > On Mon, 2014-12-22 at 11:14 +0100, Christophe Leroy wrote: > > > On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only p= ages > > > and is set to 0 for RW pages. So we should use _PAGE_RO instead of _P= AGE_RW > > >=20 > > > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > > Hi Christophe, been meaning to look over all you recent 8xx MMU/TLB pat= ches > > but got so little time :( > >=20 > > This is very cool (not sure if there will be a performance gain) but .= . > I think every saved cycle is worth it. > Before I did any modification: > * ITLBMiss was 28 instructions. > * DTLBMiss was 32 instructions. > Now, (No MODULES, no CPU6, no CPU15): > * ITLBMiss is 15 instructions > * DTLBMiss is 24 instructions I only meant this patch, sorry for not being explicit about that. > > >=20 > > >=20 > > > diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/= include/asm/pgtable-ppc32.h > > > index caf094a..b4e0c3b 100644 > > > --- a/arch/powerpc/include/asm/pgtable-ppc32.h > > > +++ b/arch/powerpc/include/asm/pgtable-ppc32.h > > > @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, > > > andc %1,%0,%5\n\ > > > or %1,%1,%6\n\ > > > /* 0x200 =3D=3D Extended encoding, bit 22 */ \ > > > - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are = set */ \ > > > + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO i= s set */ \ > > > rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ > > > - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ > > > + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ > > > + xori %3,%3,0x200\n \ > > > or %1,%3,%1\n\ > > > xori %1,%1,0x200\n" > > > " stwcx. %1,0,%4\n\ > > ... here I expected to loose the existing xori insn instead of adding o= ne? > >=20 > >=20 > Well, I could have xored the PAGE_USER bit instead, but in that case, it > is not anymore an 'or' but an 'and' that has to be performed between the > bits, and then all other bits must be set to 1, or the result of the 'and= ' shall be inserted using 'rlwimi'. So it would be more modifications than = just adding an xori, and not less instructions. >=20 I see, thanks Jocke= ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW 2015-01-06 7:03 ` leroy christophe @ 2015-01-07 1:21 ` Scott Wood -1 siblings, 0 replies; 10+ messages in thread From: Scott Wood @ 2015-01-07 1:21 UTC (permalink / raw) To: leroy christophe Cc: Joakim Tjernlund, paulus, mpe, benh, linux-kernel, linuxppc-dev On Tue, 2015-01-06 at 08:03 +0100, leroy christophe wrote: > Le 05/01/2015 19:12, Joakim Tjernlund a écrit : > > On Mon, 2014-12-22 at 11:14 +0100, Christophe Leroy wrote: > >> On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages > >> and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW > >> > >> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > > Hi Christophe, been meaning to look over all you recent 8xx MMU/TLB patches > > but got so little time :( > > > > This is very cool (not sure if there will be a performance gain) but .. > I think every saved cycle is worth it. > Before I did any modification: > * ITLBMiss was 28 instructions. > * DTLBMiss was 32 instructions. > Now, (No MODULES, no CPU6, no CPU15): > * ITLBMiss is 15 instructions > * DTLBMiss is 24 instructions > >> > >> > >> diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h > >> index caf094a..b4e0c3b 100644 > >> --- a/arch/powerpc/include/asm/pgtable-ppc32.h > >> +++ b/arch/powerpc/include/asm/pgtable-ppc32.h > >> @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, > >> andc %1,%0,%5\n\ > >> or %1,%1,%6\n\ > >> /* 0x200 == Extended encoding, bit 22 */ \ > >> - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \ > >> + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is set */ \ > >> rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ > >> - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ > >> + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ > >> + xori %3,%3,0x200\n \ > >> or %1,%3,%1\n\ > >> xori %1,%1,0x200\n" > >> " stwcx. %1,0,%4\n\ > > ... here I expected to loose the existing xori insn instead of adding one? > > > > > Well, I could have xored the PAGE_USER bit instead, but in that case, it > is not anymore an 'or' but an 'and' that has to be performed between the > bits, and then all other bits must be set to 1, or the result of the > 'and' shall be inserted using 'rlwimi'. So it would be more > modifications than just adding an xori, and not less instructions. How about "andc %3,%3,%1; rlwimi %1,%3,0,0x200" instead of the "xori, or, xori" sequence? -Scott ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW @ 2015-01-07 1:21 ` Scott Wood 0 siblings, 0 replies; 10+ messages in thread From: Scott Wood @ 2015-01-07 1:21 UTC (permalink / raw) To: leroy christophe; +Cc: linux-kernel, paulus, linuxppc-dev On Tue, 2015-01-06 at 08:03 +0100, leroy christophe wrote: > Le 05/01/2015 19:12, Joakim Tjernlund a écrit : > > On Mon, 2014-12-22 at 11:14 +0100, Christophe Leroy wrote: > >> On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages > >> and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW > >> > >> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > > Hi Christophe, been meaning to look over all you recent 8xx MMU/TLB patches > > but got so little time :( > > > > This is very cool (not sure if there will be a performance gain) but .. > I think every saved cycle is worth it. > Before I did any modification: > * ITLBMiss was 28 instructions. > * DTLBMiss was 32 instructions. > Now, (No MODULES, no CPU6, no CPU15): > * ITLBMiss is 15 instructions > * DTLBMiss is 24 instructions > >> > >> > >> diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h > >> index caf094a..b4e0c3b 100644 > >> --- a/arch/powerpc/include/asm/pgtable-ppc32.h > >> +++ b/arch/powerpc/include/asm/pgtable-ppc32.h > >> @@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p, > >> andc %1,%0,%5\n\ > >> or %1,%1,%6\n\ > >> /* 0x200 == Extended encoding, bit 22 */ \ > >> - /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \ > >> + /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is set */ \ > >> rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \ > >> - rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \ > >> + rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \ > >> + xori %3,%3,0x200\n \ > >> or %1,%3,%1\n\ > >> xori %1,%1,0x200\n" > >> " stwcx. %1,0,%4\n\ > > ... here I expected to loose the existing xori insn instead of adding one? > > > > > Well, I could have xored the PAGE_USER bit instead, but in that case, it > is not anymore an 'or' but an 'and' that has to be performed between the > bits, and then all other bits must be set to 1, or the result of the > 'and' shall be inserted using 'rlwimi'. So it would be more > modifications than just adding an xori, and not less instructions. How about "andc %3,%3,%1; rlwimi %1,%3,0,0x200" instead of the "xori, or, xori" sequence? -Scott ^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2015-01-07 1:21 UTC | newest] Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2014-12-22 10:14 [PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW Christophe Leroy 2014-12-22 10:14 ` Christophe Leroy 2015-01-05 18:12 ` Joakim Tjernlund 2015-01-05 18:12 ` Joakim Tjernlund 2015-01-06 7:03 ` leroy christophe 2015-01-06 7:03 ` leroy christophe 2015-01-06 13:05 ` Joakim Tjernlund 2015-01-06 13:05 ` Joakim Tjernlund 2015-01-07 1:21 ` Scott Wood 2015-01-07 1:21 ` Scott Wood
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