On Fri, 2017-08-04 at 16:56 +0200, Christophe Lombard wrote:
> The POWER9 core supports a new feature: ASB_Notify which requires the
> support of the Special Purpose Register: TIDR.
>
> The ASB_Notify command, generated by the AFU, will attempt to
> wake-up the host thread identified by the particular LPID:PID:TID.
>
> The special register TIDR has to be updated to with the same value
> present in the process element.
>
> If the length of the register TIDR is 64bits, the CAPI Translation
> Service Layer core (XSL9) for Power9 systems limits the size (16bits) of
> the Thread ID when it generates the ASB_Notify message adding
> PID:LPID:TID information from the context.
>
> The content of the internal kernel Thread ID (32bits) can not therefore
> be used to fulfill the register TIDR.
>
> This patch allows to avoid this limitation by adding a new interface
> for the user. The instructions mfspr/mtspr SPRN_TIDR are emulated,
> save/restore SPRs (context switch) are updated and a new feature
> (CPU_FTR_TIDR) is added to POWER9 system.
Those CPU_FTR_* are internal to the kernel. You probably also need a
feature in AT_HWCAP2 to indicate to userspace that this is supported.
Also you put the onus of allocating the TIDs onto userspace which is a
bit tricky. What happens if there are duplicate TIDs for example ? (ie,
userspace doesn't allocate it or uses a library that spawns a thread)
Ben.
>
> Signed-off-by: Christophe Lombard <clomb...@linux.vnet.ibm.com>
> ---
> arch/powerpc/include/asm/cputable.h | 4 +++-
> arch/powerpc/include/asm/emulated_ops.h | 2 ++
> arch/powerpc/include/asm/ppc-opcode.h | 4 ++++
> arch/powerpc/include/asm/processor.h | 1 +
> arch/powerpc/kernel/process.c | 8 ++++++++
> arch/powerpc/kernel/traps.c | 21 +++++++++++++++++++++
> 6 files changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/include/asm/cputable.h
> b/arch/powerpc/include/asm/cputable.h
> index d02ad93..706f668 100644
> --- a/arch/powerpc/include/asm/cputable.h
> +++ b/arch/powerpc/include/asm/cputable.h
> @@ -215,6 +215,7 @@ enum {
> #define CPU_FTR_DABRX
> LONG_ASM_CONST(0x0800000000000000)
> #define CPU_FTR_PMAO_BUG LONG_ASM_CONST(0x1000000000000000)
> #define CPU_FTR_POWER9_DD1 LONG_ASM_CONST(0x4000000000000000)
> +#define CPU_FTR_TIDR LONG_ASM_CONST(0x8000000000000000)
>
> #ifndef __ASSEMBLY__
>
> @@ -474,7 +475,8 @@ enum {
> CPU_FTR_STCX_CHECKS_ADDRESS | CPU_FTR_POPCNTB | CPU_FTR_POPCNTD | \
> CPU_FTR_CFAR | CPU_FTR_HVMODE | CPU_FTR_VMX_COPY | \
> CPU_FTR_DBELL | CPU_FTR_HAS_PPR | CPU_FTR_DAWR | \
> - CPU_FTR_ARCH_207S | CPU_FTR_TM_COMP | CPU_FTR_ARCH_300)
> + CPU_FTR_ARCH_207S | CPU_FTR_TM_COMP | CPU_FTR_ARCH_300 | \
> + CPU_FTR_TIDR)
> #define CPU_FTRS_POWER9_DD1 ((CPU_FTRS_POWER9 | CPU_FTR_POWER9_DD1) & \
> (~CPU_FTR_SAO))
> #define CPU_FTRS_CELL (CPU_FTR_USE_TB | CPU_FTR_LWSYNC | \
> diff --git a/arch/powerpc/include/asm/emulated_ops.h
> b/arch/powerpc/include/asm/emulated_ops.h
> index f00e10e..e83ad42 100644
> --- a/arch/powerpc/include/asm/emulated_ops.h
> +++ b/arch/powerpc/include/asm/emulated_ops.h
> @@ -54,6 +54,8 @@ extern struct ppc_emulated {
> #ifdef CONFIG_PPC64
> struct ppc_emulated_entry mfdscr;
> struct ppc_emulated_entry mtdscr;
> + struct ppc_emulated_entry mftidr;
> + struct ppc_emulated_entry mttidr;
> struct ppc_emulated_entry lq_stq;
> #endif
> } ppc_emulated;
> diff --git a/arch/powerpc/include/asm/ppc-opcode.h
> b/arch/powerpc/include/asm/ppc-opcode.h
> index fa9ebae..3ebc446 100644
> --- a/arch/powerpc/include/asm/ppc-opcode.h
> +++ b/arch/powerpc/include/asm/ppc-opcode.h
> @@ -241,6 +241,10 @@
> #define PPC_INST_MFSPR_DSCR_USER_MASK 0xfc1ffffe
> #define PPC_INST_MTSPR_DSCR_USER 0x7c0303a6
> #define PPC_INST_MTSPR_DSCR_USER_MASK 0xfc1ffffe
> +#define PPC_INST_MFSPR_TIDR 0x7d2452a6
> +#define PPC_INST_MFSPR_TIDR_MASK 0xfd2ffffe
> +#define PPC_INST_MTSPR_TIDR 0x7d2453a6
> +#define PPC_INST_MTSPR_TIDR_MASK 0xfd2ffffe
> #define PPC_INST_MFVSRD 0x7c000066
> #define PPC_INST_MTVSRD 0x7c000166
> #define PPC_INST_SLBFEE 0x7c0007a7
> diff --git a/arch/powerpc/include/asm/processor.h
> b/arch/powerpc/include/asm/processor.h
> index fab7ff8..58cc212 100644
> --- a/arch/powerpc/include/asm/processor.h
> +++ b/arch/powerpc/include/asm/processor.h
> @@ -329,6 +329,7 @@ struct thread_struct {
> */
> int dscr_inherit;
> unsigned long ppr; /* used to save/restore SMT priority */
> + unsigned long tidr;
> #endif
> #ifdef CONFIG_PPC_BOOK3S_64
> unsigned long tar;
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 9f3e2c9..f06ea10 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1084,6 +1084,9 @@ static inline void save_sprs(struct thread_struct *t)
> if (cpu_has_feature(CPU_FTR_DSCR))
> t->dscr = mfspr(SPRN_DSCR);
>
> + if (cpu_has_feature(CPU_FTR_TIDR))
> + t->tidr = mfspr(SPRN_TIDR);
> +
> if (cpu_has_feature(CPU_FTR_ARCH_207S)) {
> t->bescr = mfspr(SPRN_BESCR);
> t->ebbhr = mfspr(SPRN_EBBHR);
> @@ -1120,6 +1123,11 @@ static inline void restore_sprs(struct thread_struct
> *old_thread,
> mtspr(SPRN_DSCR, dscr);
> }
>
> + if (cpu_has_feature(CPU_FTR_TIDR)) {
> + if (old_thread->tidr != new_thread->tidr)
> + mtspr(SPRN_TIDR, new_thread->tidr);
> + }
> +
> if (cpu_has_feature(CPU_FTR_ARCH_207S)) {
> if (old_thread->bescr != new_thread->bescr)
> mtspr(SPRN_BESCR, new_thread->bescr);
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index bfcfd9e..b829de7 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -1141,6 +1141,25 @@ static int emulate_instruction(struct pt_regs *regs)
> mtspr(SPRN_DSCR, current->thread.dscr);
> return 0;
> }
> + /* Emulate the mfspr rD, TIDR. */
> + if (((instword & PPC_INST_MFSPR_TIDR_MASK) ==
> + PPC_INST_MFSPR_TIDR) &&
> + cpu_has_feature(CPU_FTR_TIDR)) {
> + PPC_WARN_EMULATED(mftidr, regs);
> + rd = (instword >> 21) & 0x1f;
> + regs->gpr[rd] = mfspr(SPRN_TIDR);
> + return 0;
> + }
> + /* Emulate the mtspr TIDR, rD. */
> + if (((instword & PPC_INST_MTSPR_TIDR_MASK) ==
> + PPC_INST_MTSPR_TIDR) &&
> + cpu_has_feature(CPU_FTR_TIDR)) {
> + PPC_WARN_EMULATED(mttidr, regs);
> + rd = (instword >> 21) & 0x1f;
> + current->thread.tidr = regs->gpr[rd];
> + mtspr(SPRN_TIDR, regs->gpr[rd]);
> + return 0;
> + }
> #endif
>
> return -EINVAL;
> @@ -2036,6 +2055,8 @@ struct ppc_emulated ppc_emulated = {
> #ifdef CONFIG_PPC64
> WARN_EMULATED_SETUP(mfdscr),
> WARN_EMULATED_SETUP(mtdscr),
> + WARN_EMULATED_SETUP(mftidr),
> + WARN_EMULATED_SETUP(mttidr),
> WARN_EMULATED_SETUP(lq_stq),
> #endif
> };
