[PATCH v3 2/3] Keep interrupts enabled even on soft disable
Madhavan Srinivasan
maddy at linux.vnet.ibm.com
Thu Jan 5 16:12:19 AEDT 2017
On Thursday 05 January 2017 10:25 AM, Balbir Singh wrote:
> This patch removes the disabling of interrupts
> in soft-disable mode, when interrupts are received
> (in lazy mode). The new scheme keeps the interrupts
> enabled when we receive an interrupt and does the
> following:
>
> When an external interrupt is received, we
> store the interrupt in local_paca via
> ppc_md.get_irq(). Later when interrupts are
> enabled and replayed, we reuse the stored
> interrupt and process it via generic_handle_irq
>
> NOTE: This works only for PPC_XICS at the moment
> and we'll enable it for XIVE in the future. MPIC/
> OpenPIC is not supported due to the requirement
> that external interrupts/IPIs need unique priorities.
> At the cost of adding more space in the PACA, we
> can store multiple priorities and support more
> controllers, but I think we can live with supporting
> only XICS for now and XIVE in the future.
>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Cc: Paul Mackerras <paulus at samba.org>
> Cc: Nicholas Piggin <npiggin at gmail.com>
>
> Signed-off-by: Balbir Singh <bsingharora at gmail.com>
> ---
> arch/powerpc/include/asm/paca.h | 1 +
> arch/powerpc/kernel/exceptions-64s.S | 25 +++++++++++++---
> arch/powerpc/kernel/irq.c | 55 ++++++++++++++++++++++++++++++++++--
> arch/powerpc/kernel/paca.c | 1 +
> 4 files changed, 76 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
> index 6a6792b..dcbcaa6 100644
> --- a/arch/powerpc/include/asm/paca.h
> +++ b/arch/powerpc/include/asm/paca.h
> @@ -163,6 +163,7 @@ struct paca_struct {
> #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> u64 tm_scratch; /* TM scratch area for reclaim */
> #endif
> + u32 irq; /* IRQ pending */
>
> #ifdef CONFIG_PPC_POWERNV
> /* Per-core mask tracking idle threads and a lock bit-[L][TTTTTTTT] */
> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> index d39d611..cf64bc4 100644
> --- a/arch/powerpc/kernel/exceptions-64s.S
> +++ b/arch/powerpc/kernel/exceptions-64s.S
> @@ -1273,6 +1273,23 @@ EXC_REAL_NONE(0x1800, 0x1900)
> EXC_VIRT_NONE(0x5800, 0x5900)
> #endif
>
> +/*
> + * Currently we support keeping interrupts
> + * enabled only for XICS. We can enhance this
> + * as we add support for other controllers
> + */
> +#ifdef CONFIG_PPC_XICS
> +#define MASKED_INTERRUPT_DISABLE(_H) \
> + GET_SCRATCH0(r10); \
> + std r13,PACA_EXGEN+EX_R13(r13); \
> + EXCEPTION_PROLOG_PSERIES_1(handle_irq_mask, _H);
> +#else
> +#define MASKED_INTERRUPT_DISABLE(_H) \
> + mfspr r10,SPRN_##_H##SRR1; \
> + rldicl r10,r10,48,1; /* clear MSR_EE */ \
> + rotldi r10,r10,16; \
> + mtspr SPRN_##_H##SRR1,r10;
> +#endif
>
> /*
> * An interrupt came in while soft-disabled. We set paca->irq_happened, then:
> @@ -1287,6 +1304,7 @@ EXC_VIRT_NONE(0x5800, 0x5900)
> #define MASKED_INTERRUPT(_H) \
> masked_##_H##interrupt: \
> std r11,PACA_EXGEN+EX_R11(r13); \
> + std r12,PACA_EXGEN+EX_R12(r13); \
> lbz r11,PACAIRQHAPPENED(r13); \
> or r11,r11,r10; \
> stb r11,PACAIRQHAPPENED(r13); \
> @@ -1300,10 +1318,7 @@ masked_##_H##interrupt: \
> beq 2f; \
> cmpwi r10,PACA_IRQ_HMI; \
> beq 2f; \
> - mfspr r10,SPRN_##_H##SRR1; \
> - rldicl r10,r10,48,1; /* clear MSR_EE */ \
> - rotldi r10,r10,16; \
> - mtspr SPRN_##_H##SRR1,r10; \
> + MASKED_INTERRUPT_DISABLE(_H) \
> 2: mtcrf 0x80,r9; \
> ld r9,PACA_EXGEN+EX_R9(r13); \
> ld r10,PACA_EXGEN+EX_R10(r13); \
> @@ -1321,6 +1336,8 @@ USE_FIXED_SECTION(virt_trampolines)
> MASKED_INTERRUPT()
> MASKED_INTERRUPT(H)
>
> +EXC_COMMON(handle_irq_mask, 0x500, handle_masked_irq)
> +
> #ifdef CONFIG_KVM_BOOK3S_64_HANDLER
> TRAMP_REAL_BEGIN(kvmppc_skip_interrupt)
> /*
> diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
> index a018f5c..f34f06b 100644
> --- a/arch/powerpc/kernel/irq.c
> +++ b/arch/powerpc/kernel/irq.c
> @@ -96,7 +96,6 @@ extern int tau_interrupts(int);
> #ifdef CONFIG_PPC64
>
> int distribute_irqs = 1;
> -
> static inline notrace unsigned long get_irq_happened(void)
> {
> unsigned long happened;
> @@ -498,6 +497,54 @@ static inline void check_stack_overflow(void)
> #endif
> }
>
> +#ifdef CONFIG_PPC_XICS
> +static inline notrace int get_paca_irq(void)
> +{
> + int irq;
> +
> + __asm__ __volatile__("lbz %0,%1(13)"
> + : "=r" (irq) : "i" (offsetof(struct paca_struct, irq)));
> +
> + return irq;
> +}
> +
> +static inline notrace void set_paca_irq(int irq)
> +{
> + __asm__ __volatile__("stb %0,%1(13)"
> + : : "r" (irq), "i" (offsetof(struct paca_struct, irq)));
Can we add "memory" to the clobber list, since you are writing
to PACA?
> +}
> +
> +void handle_masked_irq(struct pt_regs *regs)
> +{
> + /*
> + * TODO: Add support for XIVE as applicable
> + */
> + unsigned int irq;
> + /*
> + * NOTE, we don't use irq_enter/exit, otherwise
> + * our accounting and tracing might be incorrect.
> + */
> + irq = ppc_md.get_irq();
> +
> + /*
> + * Store away irq in PACA for replay later
> + */
> + set_paca_irq(irq);
> +}
> +
> +#else
> +
> +static inline notrace int get_paca_irq(void)
> +{
> + return -1;
> +}
> +
> +static inline notrace void set_paca_irq(int irq)
> +{
> +}
> +
> +#endif /* CONFIG_PPC_XICS */
> +
> void __do_irq(struct pt_regs *regs)
> {
> unsigned int irq;
> @@ -513,7 +560,11 @@ void __do_irq(struct pt_regs *regs)
> *
> * This will typically lower the interrupt line to the CPU
> */
> - irq = ppc_md.get_irq();
> + irq = get_paca_irq();
> + if (irq != -1)
> + set_paca_irq(-1);
> + else
> + irq = ppc_md.get_irq();
>
> /* We can hard enable interrupts now to allow perf interrupts */
> may_hard_irq_enable();
> diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
> index fa20060..2ad6108 100644
> --- a/arch/powerpc/kernel/paca.c
> +++ b/arch/powerpc/kernel/paca.c
> @@ -168,6 +168,7 @@ void __init initialise_paca(struct paca_struct *new_paca, int cpu)
> /* For now -- if we have threads this will be adjusted later */
> new_paca->tcd_ptr = &new_paca->tcd;
> #endif
> + new_paca->irq = -1;
> }
>
> /* Put the paca pointer into r13 and SPRG_PACA */
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