Messages in this thread Patch in this message | | | Date | Thu, 29 Nov 2018 16:46:00 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH v6 07/24] arm64: Make PMR part of task context |
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On Mon, Nov 12, 2018 at 11:56:58AM +0000, Julien Thierry wrote: > If ICC_PMR_EL1 is used to mask interrupts, its value should be > saved/restored whenever a task is context switched out/in or > gets an exception. > > Add PMR to the registers to save in the pt_regs struct upon kernel entry, > and restore it before ERET. Also, initialize it to a sane value when > creating new tasks.
Could you please elaborate on when this matters?
Does this actually matter for context-switch? Can we do that in a pseudo-NMI handler?
Or does this only matter for exception entry/return, and not context-switch?
Thanks, Mark.
> Signed-off-by: Julien Thierry <julien.thierry@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Dave Martin <Dave.Martin@arm.com> > --- > arch/arm64/include/asm/processor.h | 3 +++ > arch/arm64/include/asm/ptrace.h | 14 +++++++++++--- > arch/arm64/kernel/asm-offsets.c | 1 + > arch/arm64/kernel/entry.S | 13 +++++++++++++ > arch/arm64/kernel/process.c | 6 ++++++ > 5 files changed, 34 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index 6b0d4df..b2315ef 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -168,6 +168,9 @@ static inline void start_thread_common(struct pt_regs *regs, unsigned long pc) > memset(regs, 0, sizeof(*regs)); > forget_syscall(regs); > regs->pc = pc; > + > + if (system_supports_irq_prio_masking()) > + regs->pmr_save = GIC_PRIO_IRQON; > } > > static inline void start_thread(struct pt_regs *regs, unsigned long pc, > diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h > index ce6998c..0ad46f5 100644 > --- a/arch/arm64/include/asm/ptrace.h > +++ b/arch/arm64/include/asm/ptrace.h > @@ -19,6 +19,8 @@ > #ifndef __ASM_PTRACE_H > #define __ASM_PTRACE_H > > +#include <asm/cpufeature.h> > + > #include <uapi/asm/ptrace.h> > > /* Current Exception Level values, as contained in CurrentEL */ > @@ -173,7 +175,8 @@ struct pt_regs { > #endif > > u64 orig_addr_limit; > - u64 unused; // maintain 16 byte alignment > + /* Only valid when ARM64_HAS_IRQ_PRIO_MASKING is enabled. */ > + u64 pmr_save; > u64 stackframe[2]; > }; > > @@ -208,8 +211,13 @@ static inline void forget_syscall(struct pt_regs *regs) > #define processor_mode(regs) \ > ((regs)->pstate & PSR_MODE_MASK) > > -#define interrupts_enabled(regs) \ > - (!((regs)->pstate & PSR_I_BIT)) > +#define irqs_priority_unmasked(regs) \ > + (system_supports_irq_prio_masking() ? \ > + (regs)->pmr_save & GIC_PRIO_STATUS_BIT : \ > + true) > + > +#define interrupts_enabled(regs) \ > + (!((regs)->pstate & PSR_I_BIT) && irqs_priority_unmasked(regs)) > > #define fast_interrupts_enabled(regs) \ > (!((regs)->pstate & PSR_F_BIT)) > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c > index 323aeb5..bab4122 100644 > --- a/arch/arm64/kernel/asm-offsets.c > +++ b/arch/arm64/kernel/asm-offsets.c > @@ -78,6 +78,7 @@ int main(void) > DEFINE(S_ORIG_X0, offsetof(struct pt_regs, orig_x0)); > DEFINE(S_SYSCALLNO, offsetof(struct pt_regs, syscallno)); > DEFINE(S_ORIG_ADDR_LIMIT, offsetof(struct pt_regs, orig_addr_limit)); > + DEFINE(S_PMR_SAVE, offsetof(struct pt_regs, pmr_save)); > DEFINE(S_STACKFRAME, offsetof(struct pt_regs, stackframe)); > DEFINE(S_FRAME_SIZE, sizeof(struct pt_regs)); > BLANK(); > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index 039144e..eb8120e 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -249,6 +249,12 @@ alternative_else_nop_endif > msr sp_el0, tsk > .endif > > + /* Save pmr */ > +alternative_if ARM64_HAS_IRQ_PRIO_MASKING > + mrs_s x20, SYS_ICC_PMR_EL1 > + str x20, [sp, #S_PMR_SAVE] > +alternative_else_nop_endif > + > /* > * Registers that may be useful after this macro is invoked: > * > @@ -269,6 +275,13 @@ alternative_else_nop_endif > /* No need to restore UAO, it will be restored from SPSR_EL1 */ > .endif > > + /* Restore pmr */ > +alternative_if ARM64_HAS_IRQ_PRIO_MASKING > + ldr x20, [sp, #S_PMR_SAVE] > + msr_s SYS_ICC_PMR_EL1, x20 > + dsb sy > +alternative_else_nop_endif > + > ldp x21, x22, [sp, #S_PC] // load ELR, SPSR > .if \el == 0 > ct_user_enter > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index d9a4c2d..71e8850 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -231,6 +231,9 @@ void __show_regs(struct pt_regs *regs) > > printk("sp : %016llx\n", sp); > > + if (system_supports_irq_prio_masking()) > + printk("pmr_save: %08llx\n", regs->pmr_save); > + > i = top_reg; > > while (i >= 0) { > @@ -362,6 +365,9 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start, > if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE) > childregs->pstate |= PSR_SSBS_BIT; > > + if (system_supports_irq_prio_masking()) > + childregs->pmr_save = GIC_PRIO_IRQON; > + > p->thread.cpu_context.x19 = stack_start; > p->thread.cpu_context.x20 = stk_sz; > } > -- > 1.9.1 >
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