Re: [PATCH 1/4] LoongArch: Use trampoline for exception handlers and kill la.abs

From: Huacai Chen
Date: Sun Jan 15 2023 - 20:30:56 EST

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On Sat, Jan 14, 2023 at 2:38 PM Jinyang He <hejinyang@xxxxxxxxxxx> wrote:
>
> Hi, Ruoyao and Youling,
>
> I care about the performance when NUMA enabled. We set CSR.EENTRY
> for each possible cpus where is NUMA-relative. So, I guess the more
> codes in NUMA-relative memory makes more performance. If we just set
> handler_trampoline as exception handler, the performance may be
> influenced.
So copying both the handlers and handler_trampoline can solve the
problem? If that is possible, please do that on top of the latest code
in
https://github.com/loongson/linux/commits/loongarch-next

Huacai
>
>
> Thanks,
>
> Jinyang
>
>
> On 2023-01-09 17:07, Youling Tang wrote:
> > From: Xi Ruoyao <xry111@xxxxxxxxxxx>
> >
> > Use a trampoline as an exception handlers, which can kill some use of
> > la.abs in preparation for the subsequent support of the PIE kernel.
> >
> > Signed-off-by: Xi Ruoyao <xry111@xxxxxxxxxxx>
> > Signed-off-by: Youling Tang <tangyouling@xxxxxxxxxxx>
> > ---
> > arch/loongarch/include/asm/stackframe.h | 8 +++----
> > arch/loongarch/include/asm/uaccess.h | 1 -
> > arch/loongarch/kernel/entry.S | 6 +++---
> > arch/loongarch/kernel/genex.S | 20 +++++++++---------
> > arch/loongarch/kernel/head.S | 2 +-
> > arch/loongarch/kernel/traps.c | 4 +++-
> > arch/loongarch/mm/tlbex.S | 28 +++++++------------------
> > 7 files changed, 29 insertions(+), 40 deletions(-)
> >
> > diff --git a/arch/loongarch/include/asm/stackframe.h b/arch/loongarch/include/asm/stackframe.h
> > index 4ca953062b5b..96c94035b5d0 100644
> > --- a/arch/loongarch/include/asm/stackframe.h
> > +++ b/arch/loongarch/include/asm/stackframe.h
> > @@ -76,8 +76,8 @@
> > * kernelsp array for it. It stores the current sp in t0 and loads the
> > * new value in sp.
> > */
> > - .macro get_saved_sp docfi=0
> > - la.abs t1, kernelsp
> > + .macro get_saved_sp docfi=0
> > + la.pcrel t1, kernelsp
> > #ifdef CONFIG_SMP
> > csrrd t0, PERCPU_BASE_KS
> > LONG_ADD t1, t1, t0
> > @@ -89,8 +89,8 @@
> > LONG_L sp, t1, 0
> > .endm
> >
> > - .macro set_saved_sp stackp temp temp2
> > - la.abs \temp, kernelsp
> > + .macro set_saved_sp stackp temp temp2
> > + la.pcrel \temp, kernelsp
> > #ifdef CONFIG_SMP
> > LONG_ADD \temp, \temp, u0
> > #endif
> > diff --git a/arch/loongarch/include/asm/uaccess.h b/arch/loongarch/include/asm/uaccess.h
> > index 255899d4a7c3..0d22991ae430 100644
> > --- a/arch/loongarch/include/asm/uaccess.h
> > +++ b/arch/loongarch/include/asm/uaccess.h
> > @@ -22,7 +22,6 @@
> > extern u64 __ua_limit;
> >
> > #define __UA_ADDR ".dword"
> > -#define __UA_LA "la.abs"
> > #define __UA_LIMIT __ua_limit
> >
> > /*
> > diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S
> > index d53b631c9022..ca01afdbec3f 100644
> > --- a/arch/loongarch/kernel/entry.S
> > +++ b/arch/loongarch/kernel/entry.S
> > @@ -18,9 +18,9 @@
> > .text
> > .cfi_sections .debug_frame
> > .align 5
> > -SYM_FUNC_START(handle_syscall)
> > +SYM_FUNC_START(handle_sys)
> > csrrd t0, PERCPU_BASE_KS
> > - la.abs t1, kernelsp
> > + la.pcrel t1, kernelsp
> > add.d t1, t1, t0
> > move t2, sp
> > ld.d sp, t1, 0
> > @@ -66,7 +66,7 @@ SYM_FUNC_START(handle_syscall)
> > bl do_syscall
> >
> > RESTORE_ALL_AND_RET
> > -SYM_FUNC_END(handle_syscall)
> > +SYM_FUNC_END(handle_sys)
> >
> > SYM_CODE_START(ret_from_fork)
> > bl schedule_tail # a0 = struct task_struct *prev
> > diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S
> > index 75e5be807a0d..d3df0fa725a2 100644
> > --- a/arch/loongarch/kernel/genex.S
> > +++ b/arch/loongarch/kernel/genex.S
> > @@ -32,9 +32,8 @@ SYM_FUNC_START(__arch_cpu_idle)
> > SYM_FUNC_END(__arch_cpu_idle)
> >
> > SYM_FUNC_START(handle_vint)
> > - BACKUP_T0T1
> > SAVE_ALL
> > - la.abs t1, __arch_cpu_idle
> > + la.pcrel t1, __arch_cpu_idle
> > LONG_L t0, sp, PT_ERA
> > /* 32 byte rollback region */
> > ori t0, t0, 0x1f
> > @@ -43,8 +42,7 @@ SYM_FUNC_START(handle_vint)
> > LONG_S t0, sp, PT_ERA
> > 1: move a0, sp
> > move a1, sp
> > - la.abs t0, do_vint
> > - jirl ra, t0, 0
> > + bl do_vint
> > RESTORE_ALL_AND_RET
> > SYM_FUNC_END(handle_vint)
> >
> > @@ -67,12 +65,10 @@ SYM_FUNC_END(except_vec_cex)
> > .macro BUILD_HANDLER exception handler prep
> > .align 5
> > SYM_FUNC_START(handle_\exception)
> > - BACKUP_T0T1
> > SAVE_ALL
> > build_prep_\prep
> > move a0, sp
> > - la.abs t0, do_\handler
> > - jirl ra, t0, 0
> > + bl do_\handler
> > RESTORE_ALL_AND_RET
> > SYM_FUNC_END(handle_\exception)
> > .endm
> > @@ -89,7 +85,11 @@ SYM_FUNC_END(except_vec_cex)
> > BUILD_HANDLER watch watch none
> > BUILD_HANDLER reserved reserved none /* others */
> >
> > -SYM_FUNC_START(handle_sys)
> > - la.abs t0, handle_syscall
> > +SYM_FUNC_START(handler_trampoline)
> > + csrwr t0, EXCEPTION_KS0
> > + csrwr t1, EXCEPTION_KS1
> > + pcaddi t0, 0
> > + ld.d t0, t0, 16
> > jr t0
> > -SYM_FUNC_END(handle_sys)
> > + nop
> > +SYM_FUNC_END(handler_trampoline)
> > diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
> > index 57bada6b4e93..aa6181714ec3 100644
> > --- a/arch/loongarch/kernel/head.S
> > +++ b/arch/loongarch/kernel/head.S
> > @@ -117,7 +117,7 @@ SYM_CODE_START(smpboot_entry)
> > li.w t0, 0x00 # FPE=0, SXE=0, ASXE=0, BTE=0
> > csrwr t0, LOONGARCH_CSR_EUEN
> >
> > - la.abs t0, cpuboot_data
> > + la.pcrel t0, cpuboot_data
> > ld.d sp, t0, CPU_BOOT_STACK
> > ld.d tp, t0, CPU_BOOT_TINFO
> >
> > diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
> > index 7ea62faeeadb..0e8faaca3679 100644
> > --- a/arch/loongarch/kernel/traps.c
> > +++ b/arch/loongarch/kernel/traps.c
> > @@ -61,6 +61,7 @@ extern asmlinkage void handle_lasx(void);
> > extern asmlinkage void handle_reserved(void);
> > extern asmlinkage void handle_watch(void);
> > extern asmlinkage void handle_vint(void);
> > +extern asmlinkage void handler_trampoline(void);
> >
> > static void show_backtrace(struct task_struct *task, const struct pt_regs *regs,
> > const char *loglvl, bool user)
> > @@ -716,7 +717,8 @@ void per_cpu_trap_init(int cpu)
> > /* Install CPU exception handler */
> > void set_handler(unsigned long offset, void *addr, unsigned long size)
> > {
> > - memcpy((void *)(eentry + offset), addr, size);
> > + memcpy((void *)(eentry + offset), &handler_trampoline, 24);
> > + memcpy((void *)(eentry + offset + 24), &addr, 8);
> > local_flush_icache_range(eentry + offset, eentry + offset + size);
> > }
> >
> > diff --git a/arch/loongarch/mm/tlbex.S b/arch/loongarch/mm/tlbex.S
> > index 58781c6e4191..cfaacdac518c 100644
> > --- a/arch/loongarch/mm/tlbex.S
> > +++ b/arch/loongarch/mm/tlbex.S
> > @@ -24,8 +24,7 @@
> > move a0, sp
> > REG_S a2, sp, PT_BVADDR
> > li.w a1, \write
> > - la.abs t0, do_page_fault
> > - jirl ra, t0, 0
> > + bl do_page_fault
> > RESTORE_ALL_AND_RET
> > SYM_FUNC_END(tlb_do_page_fault_\write)
> > .endm
> > @@ -34,20 +33,16 @@
> > tlb_do_page_fault 1
> >
> > SYM_FUNC_START(handle_tlb_protect)
> > - BACKUP_T0T1
> > SAVE_ALL
> > move a0, sp
> > move a1, zero
> > csrrd a2, LOONGARCH_CSR_BADV
> > REG_S a2, sp, PT_BVADDR
> > - la.abs t0, do_page_fault
> > - jirl ra, t0, 0
> > + bl do_page_fault
> > RESTORE_ALL_AND_RET
> > SYM_FUNC_END(handle_tlb_protect)
> >
> > SYM_FUNC_START(handle_tlb_load)
> > - csrwr t0, EXCEPTION_KS0
> > - csrwr t1, EXCEPTION_KS1
> > csrwr ra, EXCEPTION_KS2
> >
> > /*
> > @@ -116,7 +111,7 @@ smp_pgtable_change_load:
> >
> > #ifdef CONFIG_64BIT
> > vmalloc_load:
> > - la.abs t1, swapper_pg_dir
> > + la.pcrel t1, swapper_pg_dir
> > b vmalloc_done_load
> > #endif
> >
> > @@ -187,13 +182,10 @@ tlb_huge_update_load:
> > nopage_tlb_load:
> > dbar 0
> > csrrd ra, EXCEPTION_KS2
> > - la.abs t0, tlb_do_page_fault_0
> > - jr t0
> > + b tlb_do_page_fault_0
> > SYM_FUNC_END(handle_tlb_load)
> >
> > SYM_FUNC_START(handle_tlb_store)
> > - csrwr t0, EXCEPTION_KS0
> > - csrwr t1, EXCEPTION_KS1
> > csrwr ra, EXCEPTION_KS2
> >
> > /*
> > @@ -263,7 +255,7 @@ smp_pgtable_change_store:
> >
> > #ifdef CONFIG_64BIT
> > vmalloc_store:
> > - la.abs t1, swapper_pg_dir
> > + la.pcrel t1, swapper_pg_dir
> > b vmalloc_done_store
> > #endif
> >
> > @@ -336,13 +328,10 @@ tlb_huge_update_store:
> > nopage_tlb_store:
> > dbar 0
> > csrrd ra, EXCEPTION_KS2
> > - la.abs t0, tlb_do_page_fault_1
> > - jr t0
> > + b tlb_do_page_fault_1
> > SYM_FUNC_END(handle_tlb_store)
> >
> > SYM_FUNC_START(handle_tlb_modify)
> > - csrwr t0, EXCEPTION_KS0
> > - csrwr t1, EXCEPTION_KS1
> > csrwr ra, EXCEPTION_KS2
> >
> > /*
> > @@ -411,7 +400,7 @@ smp_pgtable_change_modify:
> >
> > #ifdef CONFIG_64BIT
> > vmalloc_modify:
> > - la.abs t1, swapper_pg_dir
> > + la.pcrel t1, swapper_pg_dir
> > b vmalloc_done_modify
> > #endif
> >
> > @@ -483,8 +472,7 @@ tlb_huge_update_modify:
> > nopage_tlb_modify:
> > dbar 0
> > csrrd ra, EXCEPTION_KS2
> > - la.abs t0, tlb_do_page_fault_1
> > - jr t0
> > + b tlb_do_page_fault_1
> > SYM_FUNC_END(handle_tlb_modify)
> >
> > SYM_FUNC_START(handle_tlb_refill)
>

Next message: Stephen Rothwell: "Re: linux-next: duplicate patch in the rcu tree"
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In reply to: Jinyang He: "Re: [PATCH 1/4] LoongArch: Use trampoline for exception handlers and kill la.abs"
Next in thread: Youling Tang: "[PATCH 3/4] LoongArch: Add support for kernel relocation"
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