On Wed, 2010-10-13 at 11:52 +1100, Michael Neuling wrote:
> In message <1286855108.14049.8.ca...@flin.austin.ibm.com> you wrote:
> > icswx is a PowerPC co-processor instruction to send data to a
> > co-processor. On Book-S processors the LPAR_ID and process ID (PID) of
> > the owning process are registered in the window context of the
> > co-processor at initial time. When the icswx instruction is executed,
> > the L2 generates a cop-reg transaction on PowerBus. The transaction has
> > no address and the processor does not perform an MMU access to
> > authenticate the transaction. The coprocessor compares the LPAR_ID and
> > the PID included in the transaction and the LPAR_ID and PID held in the
> > window context to determine if the process is authorized to generate the
> > transaction.
> >
> > This patch adds icswx co-processor instruction support.
>
> Can you describe the ABI a bit?
>
> How has this changed from version 1?
>
The icswx instruction itself does nothing but generating a cop-req
transaction on PowerBus. The cop-req transaction causes 1 cache
line of data (128 bytes) sent to the co-processor. This provides
a low latency mechanism for sending small amount of data without
the co-processor becoming a master on the PowerBus.
Since the transaction has no address and the processor does not
perform an MMU access to authenticate the transaction, the
co-processor relys on the the LPAR_ID and PID to determine if
the process is authorized to generate the transaction.
The OS needs to assign a 16-bit PID for the process. This
cop-PID needs needs to be updated during context switch. The
cop-PID needs to be destroied when the context is destroied.
Change log from v1:
- Change 2'nd parameter of use_cop() from struct task_struct *task
to struct mm_struct *mm.
- Check for mm == current->active_mm before calling mtspr().
- Add a lock to guard acop related operations.
- Check for POWER7 CPU.
- Move the definition of SPRN_PID from reg_booke.h to avoid
defining SPRN_PID in two different files.
- Rename pid to acop_pid.
- Change function name disuse_cop() to drop_cop().
- Add a comment to describe the two new fields in mm_context_t.
- Moving CONFIG_ICSWX from arch/powerpc/platforms/pseries/Kconfig
to arch/powerpc/platforms/Kconfig.cputype
All other comments will be addressed in a new patch.
> Patch has been whitespace munged aswell.
>
> More comments below...
>
> >
> > Signed-off-by: Sonny Rao <sonny...@linux.vnet.ibm.com>
> > Signed-off-by: Tseng-Hui (Frank) Lin <th...@linux.vnet.ibm.com>
> > ---
> > arch/powerpc/include/asm/mmu-hash64.h | 5 ++
> > arch/powerpc/include/asm/mmu_context.h | 6 ++
> > arch/powerpc/include/asm/reg.h | 12 ++++
> > arch/powerpc/include/asm/reg_booke.h | 3 -
> > arch/powerpc/mm/mmu_context_hash64.c | 105
> > ++++++++++++++++++++++++++++++++
> > arch/powerpc/platforms/Kconfig.cputype | 16 +++++
> > 6 files changed, 144 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/mmu-hash64.h
> > b/arch/powerpc/include/asm/mmu-hash64.h
> > index acac35d..6c1ab90 100644
> > --- a/arch/powerpc/include/asm/mmu-hash64.h
> > +++ b/arch/powerpc/include/asm/mmu-hash64.h
> > @@ -423,6 +423,11 @@ typedef struct {
> > #ifdef CONFIG_PPC_SUBPAGE_PROT
> > struct subpage_prot_table spt;
> > #endif /* CONFIG_PPC_SUBPAGE_PROT */
> > +#ifdef CONFIG_ICSWX
> > + unsigned long acop; /* mask of enabled coprocessor types */
> > +#define HASH64_MAX_PID (0xFFFF)
> > + unsigned int acop_pid; /* pid value used with coprocessors */
> > +#endif /* CONFIG_ICSWX */
> > } mm_context_t;
> >
> >
> > diff --git a/arch/powerpc/include/asm/mmu_context.h
> > b/arch/powerpc/include/asm/mmu_context.h
> > index 81fb412..88118de 100644
> > --- a/arch/powerpc/include/asm/mmu_context.h
> > +++ b/arch/powerpc/include/asm/mmu_context.h
> > @@ -80,6 +80,12 @@ static inline void switch_mm(struct mm_struct *prev,
> > struct mm_struct *next,
> >
> > #define deactivate_mm(tsk,mm) do { } while (0)
> >
> > +#ifdef CONFIG_ICSWX
> > +extern void switch_cop(struct mm_struct *next);
> > +extern int use_cop(unsigned long acop, struct mm_struct *mm);
> > +extern void drop_cop(unsigned long acop, struct mm_struct *mm);
> > +#endif /* CONFIG_ICSWX */
> > +
> > /*
> > * After we have set current->mm to a new value, this activates
> > * the context for the new mm so we see the new mappings.
> > diff --git a/arch/powerpc/include/asm/reg.h
> > b/arch/powerpc/include/asm/reg.h
> > index ff0005eec..9bbf178 100644
> > --- a/arch/powerpc/include/asm/reg.h
> > +++ b/arch/powerpc/include/asm/reg.h
> > @@ -170,8 +170,19 @@
> > #define SPEFSCR_FRMC 0x00000003 /* Embedded FP rounding mode co
> ntrol
> > */
> >
> > /* Special Purpose Registers (SPRNs)*/
> > +
> > +#ifdef CONFIG_40x
> > +#define SPRN_PID 0x3B1 /* Process ID */
> > +#else
> > +#define SPRN_PID 0x030 /* Process ID */
> > +#ifdef CONFIG_BOOKE
> > +#define SPRN_PID0 SPRN_PID/* Process ID Register 0 */
> > +#endif
> > +#endif
> > +
>
> Why are you moving these definitions?
>
> > #define SPRN_CTR 0x009 /* Count Register */
> > #define SPRN_DSCR 0x11
> > +#define SPRN_ACOP 0x1F /* Available Coprocessor Register */
> > #define SPRN_CTRLF 0x088
> > #define SPRN_CTRLT 0x098
> > #define CTRL_CT 0xc0000000 /* current thread */
> > @@ -879,6 +890,7 @@
> > #define PV_POWER5 0x003A
> > #define PV_POWER5p 0x003B
> > #define PV_970FX 0x003C
> > +#define PV_POWER7 0x003F
> > #define PV_630 0x0040
> > #define PV_630p 0x0041
> > #define PV_970MP 0x0044
> > diff --git a/arch/powerpc/include/asm/reg_booke.h
> > b/arch/powerpc/include/asm/reg_booke.h
> > index 667a498..5b0c781 100644
> > --- a/arch/powerpc/include/asm/reg_booke.h
> > +++ b/arch/powerpc/include/asm/reg_booke.h
> > @@ -150,8 +150,6 @@
> > * or IBM 40x.
> > */
> > #ifdef CONFIG_BOOKE
> > -#define SPRN_PID 0x030 /* Process ID */
> > -#define SPRN_PID0 SPRN_PID/* Process ID Register 0 */
> > #define SPRN_CSRR0 0x03A /* Critical Save and Restore Register 0 */
> > #define SPRN_CSRR1 0x03B /* Critical Save and Restore Register 1 */
> > #define SPRN_DEAR 0x03D /* Data Error Address Register */
> > @@ -168,7 +166,6 @@
> > #define SPRN_TCR 0x154 /* Timer Control Register */
> > #endif /* Book E */
> > #ifdef CONFIG_40x
> > -#define SPRN_PID 0x3B1 /* Process ID */
> > #define SPRN_DBCR1 0x3BD /* Debug Control Register 1 */
> > #define SPRN_ESR 0x3D4 /* Exception Syndrome Register */
> > #define SPRN_DEAR 0x3D5 /* Data Error Address Register */
> > diff --git a/arch/powerpc/mm/mmu_context_hash64.c
> > b/arch/powerpc/mm/mmu_context_hash64.c
> > index 2535828..8f432b6 100644
> > --- a/arch/powerpc/mm/mmu_context_hash64.c
> > +++ b/arch/powerpc/mm/mmu_context_hash64.c
> > @@ -18,6 +18,7 @@
> > #include <linux/mm.h>
> > #include <linux/spinlock.h>
> > #include <linux/idr.h>
> > +#include <linux/percpu.h>
> > #include <linux/module.h>
> > #include <linux/gfp.h>
> >
> > @@ -26,6 +27,103 @@
> > static DEFINE_SPINLOCK(mmu_context_lock);
> > static DEFINE_IDA(mmu_context_ida);
> >
> > +#ifdef CONFIG_ICSWX
> > +static DEFINE_SPINLOCK(mmu_context_acop_lock);
> > +static DEFINE_IDA(cop_ida);
> > +
> > +/* Lazy switch the ACOP register */
> > +static DEFINE_PER_CPU(unsigned long, acop_reg);
> > +
> > +void switch_cop(struct mm_struct *next)
> > +{
> > + if (!__is_processor(PV_POWER7))
> > + return;
> > +
> > + mtspr(SPRN_PID, next->context.acop_pid);
> > + if (next->context.acop_pid &&
> > + __get_cpu_var(acop_reg) != next->context.acop) {
> > + mtspr(SPRN_ACOP, next->context.acop);
> > + __get_cpu_var(acop_reg) = next->context.acop;
> > + }
> > +}
> > +EXPORT_SYMBOL(switch_cop);
> > +
> > +int use_cop(unsigned long acop, struct mm_struct *mm)
> > +{
> > + int acop_pid;
> > + int err;
> > +
> > + if (!__is_processor(PV_POWER7))
> > + return -ENOSYS;
>
> This should be a CPU feature.
>
> > +
> > + if (!mm)
> > + return -EINVAL;
> > +
> > + if (!mm->context.acop_pid) {
> > + if (!ida_pre_get(&cop_ida, GFP_KERNEL))
> > + return -ENOMEM;
> > +again:
> > + spin_lock(&mmu_context_acop_lock);
> > + err = ida_get_new_above(&cop_ida, 1, &acop_pid);
> > + spin_unlock(&mmu_context_acop_lock);
> > +
> > + if (err == -EAGAIN)
> > + goto again;
>
> Make this a do while loop. Please don't create your own loop
> prematives.
>
> > + else if (err)
> > + return err;
> > +
> > + if (acop_pid > HASH64_MAX_PID) {
> > + spin_lock(&mmu_context_acop_lock);
> > + ida_remove(&cop_ida, acop_pid);
> > + spin_unlock(&mmu_context_acop_lock);
> > + return -EBUSY;
> > + }
> > + mm->context.acop_pid = acop_pid;
> > + if (mm == current->active_mm)
> > + mtspr(SPRN_PID, mm->context.acop_pid);
> > + }
> > + spin_lock(&mmu_context_acop_lock);
> > + mm->context.acop |= acop;
> > + spin_unlock(&mmu_context_acop_lock);
> > +
> > + get_cpu_var(acop_reg) = mm->context.acop;
> > + if (mm == current->active_mm)
> > + mtspr(SPRN_ACOP, mm->context.acop);
> > + put_cpu_var(acop_reg);
> > +
> > + return mm->context.acop_pid;
> > +}
> > +EXPORT_SYMBOL(use_cop);
> > +
> > +void drop_cop(unsigned long acop, struct mm_struct *mm)
> > +{
> > + if (!__is_processor(PV_POWER7))
> > + return;
> > +
> > + if (WARN_ON(!mm))
> > + return;
> > +
> > + spin_lock(&mmu_context_acop_lock);
> > + mm->context.acop &= ~acop;
> > + spin_unlock(&mmu_context_acop_lock);
> > + if (!mm->context.acop) {
> > + spin_lock(&mmu_context_acop_lock);
> > + ida_remove(&cop_ida, mm->context.acop_pid);
> > + spin_unlock(&mmu_context_acop_lock);
> > + mm->context.acop_pid = 0;
> > + if (mm == current->active_mm)
> > + mtspr(SPRN_PID, mm->context.acop_pid);
> > + } else {
> > + get_cpu_var(acop_reg) = mm->context.acop;
> > + if (mm == current->active_mm)
> > + mtspr(SPRN_ACOP, mm->context.acop);
> > + put_cpu_var(acop_reg);
> > + }
> > + mmput(mm);
> > +}
> > +EXPORT_SYMBOL(drop_cop);
> > +#endif /* CONFIG_ICSWX */
> > +
> > /*
> > * The proto-VSID space has 2^35 - 1 segments available for user
> > mappings.
> > * Each segment contains 2^28 bytes. Each context maps 2^44 bytes,
> > @@ -93,6 +191,13 @@ EXPORT_SYMBOL_GPL(__destroy_context);
> >
> > void destroy_context(struct mm_struct *mm)
> > {
> > +#ifdef CONFIG_ICSWX
> > + if (mm->context.acop_pid) {
> > + spin_lock(&mmu_context_acop_lock);
> > + ida_remove(&cop_ida, mm->context.acop_pid);
> > + spin_unlock(&mmu_context_acop_lock);
> > + }
> > +#endif /* CONFIG_ICSWX */
>
> Can you put this in a destroy_context_acop() and #define that funtion
> based CONFIG_ICSWX. Cleans up the #ifdefs here
>
>
> > __destroy_context(mm->context.id);
> > subpage_prot_free(mm);
> > mm->context.id = NO_CONTEXT;
> > diff --git a/arch/powerpc/platforms/Kconfig.cputype
> > b/arch/powerpc/platforms/Kconfig.cputype
> > index d361f81..9674703 100644
> > --- a/arch/powerpc/platforms/Kconfig.cputype
> > +++ b/arch/powerpc/platforms/Kconfig.cputype
> > @@ -220,6 +220,22 @@ config VSX
> >
> > If in doubt, say Y here.
> >
> > +config ICSWX
> > + bool "Support for PowerPC icswx co-processor instruction"
> > + depends on POWER4
> > + default n
> > + ---help---
> > +
> > + Enabling this option to turn on the PowerPC icswx co-processor
> > + instruction support for POWER7 processors.
> > + This option is only useful if you have a processor that supports
> > + icswx co-processor instruction. It does not have any affect on
> > + processors without icswx co-processor instruction.
> > +
> > + This support slightly increases kernel memory usage.
> > +
> > + Say N if you do not have a POWER7 processor and a PowerPC
> > co-processor.
> > +
> > config SPE
> > bool "SPE Support"
> > depends on E200 || (E500 && !PPC_E500MC)
> >
> >
> > _______________________________________________
> > Linuxppc-dev mailing list
> > Linuxppc-dev@lists.ozlabs.org
> > https://lists.ozlabs.org/listinfo/linuxppc-dev
> >
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