Re: [kvm-unit-tests PATCH v2 2/3] riscv: lib: Add SSE assembly entry handling

[Andrew Jones <andrew.jones@linux.dev>]

On Fri, Nov 22, 2024 at 03:04:56PM +0100, Clément Léger wrote:
> Add a SSE entry assembly code to handle SSE events. Events should be
> registered with a struct sse_handler_arg containing a correct stack and
> handler function.
> 
> Signed-off-by: Clément Léger <cleger@rivosinc.com>
> ---
>  riscv/Makefile          |   1 +
>  lib/riscv/asm/sse.h     |  16 +++++++
>  lib/riscv/sse-entry.S   | 100 ++++++++++++++++++++++++++++++++++++++++

Let's just add the entry function to riscv/sbi-asm.S and the
sse_handler_arg struct definition to riscv/sbi-tests.h

>  lib/riscv/asm-offsets.c |   9 ++++
>  4 files changed, 126 insertions(+)
>  create mode 100644 lib/riscv/asm/sse.h
>  create mode 100644 lib/riscv/sse-entry.S
> 
> diff --git a/riscv/Makefile b/riscv/Makefile
> index 28b04156..e50621ad 100644
> --- a/riscv/Makefile
> +++ b/riscv/Makefile
> @@ -39,6 +39,7 @@ cflatobjs += lib/riscv/sbi.o
>  cflatobjs += lib/riscv/setjmp.o
>  cflatobjs += lib/riscv/setup.o
>  cflatobjs += lib/riscv/smp.o
> +cflatobjs += lib/riscv/sse-entry.o
>  cflatobjs += lib/riscv/stack.o
>  cflatobjs += lib/riscv/timer.o
>  ifeq ($(ARCH),riscv32)
> diff --git a/lib/riscv/asm/sse.h b/lib/riscv/asm/sse.h
> new file mode 100644
> index 00000000..557f6680
> --- /dev/null
> +++ b/lib/riscv/asm/sse.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef _ASMRISCV_SSE_H_
> +#define _ASMRISCV_SSE_H_
> +
> +typedef void (*sse_handler_fn)(void *data, struct pt_regs *regs, unsigned int hartid);
> +
> +struct sse_handler_arg {
> +	unsigned long reg_tmp;
> +	sse_handler_fn handler;
> +	void *handler_data;
> +	void *stack;
> +};
> +
> +extern void sse_entry(void);
> +
> +#endif /* _ASMRISCV_SSE_H_ */
> diff --git a/lib/riscv/sse-entry.S b/lib/riscv/sse-entry.S
> new file mode 100644
> index 00000000..bedc47e9
> --- /dev/null
> +++ b/lib/riscv/sse-entry.S
> @@ -0,0 +1,100 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * SBI SSE entry code
> + *
> + * Copyright (C) 2024, Rivos Inc., Clément Léger <cleger@rivosinc.com>
> + */
> +#include <asm/asm.h>
> +#include <asm/asm-offsets.h>
> +#include <asm/csr.h>
> +
> +.global sse_entry
> +sse_entry:
> +	/* Save stack temporarily */
> +	REG_S sp, SSE_REG_TMP(a6)
> +	/* Set entry stack */
> +	REG_L sp, SSE_HANDLER_STACK(a6)
> +
> +	addi sp, sp, -(PT_SIZE)
> +	REG_S ra, PT_RA(sp)
> +	REG_S s0, PT_S0(sp)
> +	REG_S s1, PT_S1(sp)
> +	REG_S s2, PT_S2(sp)
> +	REG_S s3, PT_S3(sp)
> +	REG_S s4, PT_S4(sp)
> +	REG_S s5, PT_S5(sp)
> +	REG_S s6, PT_S6(sp)
> +	REG_S s7, PT_S7(sp)
> +	REG_S s8, PT_S8(sp)
> +	REG_S s9, PT_S9(sp)
> +	REG_S s10, PT_S10(sp)
> +	REG_S s11, PT_S11(sp)
> +	REG_S tp, PT_TP(sp)
> +	REG_S t0, PT_T0(sp)
> +	REG_S t1, PT_T1(sp)
> +	REG_S t2, PT_T2(sp)
> +	REG_S t3, PT_T3(sp)
> +	REG_S t4, PT_T4(sp)
> +	REG_S t5, PT_T5(sp)
> +	REG_S t6, PT_T6(sp)
> +	REG_S gp, PT_GP(sp)
> +	REG_S a0, PT_A0(sp)
> +	REG_S a1, PT_A1(sp)
> +	REG_S a2, PT_A2(sp)
> +	REG_S a3, PT_A3(sp)
> +	REG_S a4, PT_A4(sp)
> +	REG_S a5, PT_A5(sp)
> +	csrr a1, CSR_SEPC
> +	REG_S a1, PT_EPC(sp)
> +	csrr a2, CSR_SSTATUS
> +	REG_S a2, PT_STATUS(sp)
> +
> +	REG_L a0, SSE_REG_TMP(a6)
> +	REG_S a0, PT_SP(sp)
> +
> +	REG_L t0, SSE_HANDLER(a6)
> +	REG_L a0, SSE_HANDLER_DATA(a6)
> +	move a1, sp
> +	move a2, a7

nit: prefer 'mv'

> +	jalr t0
> +
> +
> +	REG_L a1, PT_EPC(sp)
> +	REG_L a2, PT_STATUS(sp)
> +	csrw CSR_SEPC, a1
> +	csrw CSR_SSTATUS, a2
> +
> +	REG_L ra, PT_RA(sp)
> +	REG_L s0, PT_S0(sp)
> +	REG_L s1, PT_S1(sp)
> +	REG_L s2, PT_S2(sp)
> +	REG_L s3, PT_S3(sp)
> +	REG_L s4, PT_S4(sp)
> +	REG_L s5, PT_S5(sp)
> +	REG_L s6, PT_S6(sp)
> +	REG_L s7, PT_S7(sp)
> +	REG_L s8, PT_S8(sp)
> +	REG_L s9, PT_S9(sp)
> +	REG_L s10, PT_S10(sp)
> +	REG_L s11, PT_S11(sp)
> +	REG_L tp, PT_TP(sp)
> +	REG_L t0, PT_T0(sp)
> +	REG_L t1, PT_T1(sp)
> +	REG_L t2, PT_T2(sp)
> +	REG_L t3, PT_T3(sp)
> +	REG_L t4, PT_T4(sp)
> +	REG_L t5, PT_T5(sp)
> +	REG_L t6, PT_T6(sp)
> +	REG_L gp, PT_GP(sp)
> +	REG_L a0, PT_A0(sp)
> +	REG_L a1, PT_A1(sp)
> +	REG_L a2, PT_A2(sp)
> +	REG_L a3, PT_A3(sp)
> +	REG_L a4, PT_A4(sp)
> +	REG_L a5, PT_A5(sp)
> +
> +	REG_L sp, PT_SP(sp)
> +
> +	li a7, ASM_SBI_EXT_SSE
> +	li a6, ASM_SBI_EXT_SSE_COMPLETE
> +	ecall
> diff --git a/lib/riscv/asm-offsets.c b/lib/riscv/asm-offsets.c
> index 6c511c14..b3465eeb 100644
> --- a/lib/riscv/asm-offsets.c
> +++ b/lib/riscv/asm-offsets.c
> @@ -3,7 +3,9 @@
>  #include <elf.h>
>  #include <asm/processor.h>
>  #include <asm/ptrace.h>
> +#include <asm/sbi.h>
>  #include <asm/smp.h>
> +#include <asm/sse.h>
>  
>  int main(void)
>  {
> @@ -63,5 +65,12 @@ int main(void)
>  	OFFSET(THREAD_INFO_HARTID, thread_info, hartid);
>  	DEFINE(THREAD_INFO_SIZE, sizeof(struct thread_info));
>  
> +	OFFSET(SSE_REG_TMP, sse_handler_arg, reg_tmp);
> +	OFFSET(SSE_HANDLER, sse_handler_arg, handler);
> +	OFFSET(SSE_HANDLER_DATA, sse_handler_arg, handler_data);
> +	OFFSET(SSE_HANDLER_STACK, sse_handler_arg, stack);
> +	DEFINE(ASM_SBI_EXT_SSE, SBI_EXT_SSE);
> +	DEFINE(ASM_SBI_EXT_SSE_COMPLETE, SBI_EXT_SSE_COMPLETE);

sbi_hsm_check just uses the numbers and adds comments. We could instead
move the extension IDs from an enum to defines outside the
#ifndef __ASSEMBLY__ and function IDs can also be defines accessible
by assembly.

> +
>  	return 0;
>  }
> -- 
> 2.45.2
>

Thanks,
drew