On Sat, Mar 20, 2021 at 11:22:27PM +1100, Michael Ellerman wrote: > From: Christophe Leroy <christophe.le...@csgroup.eu> > > call_do_irq() and call_do_softirq() are simple enough to be > worth inlining. > > Inlining them avoids an mflr/mtlr pair plus a save/reload on stack. It > also allows GCC to keep the saved ksp_limit in an nonvolatile reg. > > This is inspired from S390 arch. Several other arches do more or > less the same. The way sparc arch does seems odd thought. > > Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu> > Signed-off-by: Michael Ellerman <m...@ellerman.id.au> > --- > > v2: no change. > v3: no change. > v4: > - comment reminding the purpose of the inline asm block. > - added r2 as clobbered reg > v5: > - Limiting the change to PPC32 for now. > - removed r2 from the clobbered regs list (on PPC32 r2 points to current all > the time) > - Removed patch 1 and merged ksp_limit handling in here. > v6: > - Rebase on top of merge-test (ca6e327fefb2). > - Remove the ksp_limit stuff as it's doesn't exist anymore. > > v7: > mpe: > - Enable for 64-bit too. This all in-kernel code calling in-kernel > code, and must use the kernel TOC. > - Use named parameters for the inline asm. > - Reformat inline asm. > - Mark as always_inline. > - Drop unused ret from call_do_softirq(), add r3 as clobbered. > --- > arch/powerpc/include/asm/irq.h | 2 -- > arch/powerpc/kernel/irq.c | 41 ++++++++++++++++++++++++++++++++++ > arch/powerpc/kernel/misc_32.S | 25 --------------------- > arch/powerpc/kernel/misc_64.S | 22 ------------------ > 4 files changed, 41 insertions(+), 49 deletions(-) > > diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h > index f3f264e441a7..b2bd58830430 100644 > --- a/arch/powerpc/include/asm/irq.h > +++ b/arch/powerpc/include/asm/irq.h > @@ -53,8 +53,6 @@ extern void *mcheckirq_ctx[NR_CPUS]; > extern void *hardirq_ctx[NR_CPUS]; > extern void *softirq_ctx[NR_CPUS]; > > -void call_do_softirq(void *sp); > -void call_do_irq(struct pt_regs *regs, void *sp); > extern void do_IRQ(struct pt_regs *regs); > extern void __init init_IRQ(void); > extern void __do_irq(struct pt_regs *regs); > diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c > index 5b72abbff96c..260effc0a435 100644 > --- a/arch/powerpc/kernel/irq.c > +++ b/arch/powerpc/kernel/irq.c > @@ -667,6 +667,47 @@ static inline void check_stack_overflow(void) > } > } > > +static __always_inline void call_do_softirq(const void *sp) > +{ > + /* Temporarily switch r1 to sp, call __do_softirq() then restore r1. */ > + asm volatile ( > + PPC_STLU " %%r1, %[offset](%[sp]) ;" > + "mr %%r1, %[sp] ;" > + "bl %[callee] ;" > + PPC_LL " %%r1, 0(%%r1) ;" > + : // Outputs > + : // Inputs > + [sp] "b" (sp), [offset] "i" (THREAD_SIZE - > STACK_FRAME_OVERHEAD), > + [callee] "i" (__do_softirq) > + : // Clobbers > + "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6", > + "cr7", "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10", > + "r11", "r12" > + ); > +} > + > +static __always_inline void call_do_irq(struct pt_regs *regs, void *sp) > +{ > + register unsigned long r3 asm("r3") = (unsigned long)regs; > + > + /* Temporarily switch r1 to sp, call __do_irq() then restore r1. */ > + asm volatile ( > + PPC_STLU " %%r1, %[offset](%[sp]) ;" > + "mr %%r1, %[sp] ;" > + "bl %[callee] ;" > + PPC_LL " %%r1, 0(%%r1) ;" > + : // Outputs > + "+r" (r3) > + : // Inputs > + [sp] "b" (sp), [offset] "i" (THREAD_SIZE - > STACK_FRAME_OVERHEAD), > + [callee] "i" (__do_irq) > + : // Clobbers > + "lr", "xer", "ctr", "memory", "cr0", "cr1", "cr5", "cr6", > + "cr7", "r0", "r4", "r5", "r6", "r7", "r8", "r9", "r10", > + "r11", "r12" > + ); > +} > + > void __do_irq(struct pt_regs *regs) > { > unsigned int irq; > diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S > index acc410043b96..6a076bef2932 100644 > --- a/arch/powerpc/kernel/misc_32.S > +++ b/arch/powerpc/kernel/misc_32.S > @@ -27,31 +27,6 @@ > > .text > > -_GLOBAL(call_do_softirq) > - mflr r0 > - stw r0,4(r1) > - stwu r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3) > - mr r1,r3 > - bl __do_softirq > - lwz r1,0(r1) > - lwz r0,4(r1) > - mtlr r0 > - blr > - > -/* > - * void call_do_irq(struct pt_regs *regs, void *sp); > - */ > -_GLOBAL(call_do_irq) > - mflr r0 > - stw r0,4(r1) > - stwu r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r4) > - mr r1,r4 > - bl __do_irq > - lwz r1,0(r1) > - lwz r0,4(r1) > - mtlr r0 > - blr > - > /* > * This returns the high 64 bits of the product of two 64-bit numbers. > */ > diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S > index 070465825c21..4b761a18a74d 100644 > --- a/arch/powerpc/kernel/misc_64.S > +++ b/arch/powerpc/kernel/misc_64.S > @@ -27,28 +27,6 @@ > > .text > > -_GLOBAL(call_do_softirq) > - mflr r0 > - std r0,16(r1) > - stdu r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3) > - mr r1,r3 > - bl __do_softirq > - ld r1,0(r1) > - ld r0,16(r1) > - mtlr r0 > - blr > - > -_GLOBAL(call_do_irq) > - mflr r0 > - std r0,16(r1) > - stdu r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r4) > - mr r1,r4 > - bl __do_irq > - ld r1,0(r1) > - ld r0,16(r1) > - mtlr r0 > - blr > - > _GLOBAL(__bswapdi2) > EXPORT_SYMBOL(__bswapdi2) > srdi r8,r3,32 > -- > 2.25.1 >
This change caused our ppc44x_defconfig builds to hang when powering down in QEMU: https://github.com/ClangBuiltLinux/continuous-integration2/runs/2304364629?check_suite_focus=true#logs This is probably something with clang given that GCC 10.3.0 works fine but due to the nature of the change, I have no idea how to tell what is going wrong. I tried to do some rudimentary debugging with gdb but that did not really get me anywhere. The kernel was built with just 'CC=clang' and it is reproducible with all versions of clang that the kernel supports. The QEMU invocation is visible at the link above, it is done with our boot-qemu.sh in this repo, which also houses the rootfs: https://github.com/ClangBuiltLinux/boot-utils Happy to provide any other information or debug/test as directed! Cheers, Nathan