linux-kernel - [PATCH 0/2] RISC-V: turn sbi

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Message-ID: <20250612145754.2126147-2-rkrcmar@ventanamicro.com>
Date: Thu, 12 Jun 2025 16:57:53 +0200
From: Radim Krčmář <rkrcmar@...tanamicro.com>
To: linux-riscv@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alex@...ti.fr>,
	Atish Patra <atishp@...osinc.com>,
	Andrew Jones <ajones@...tanamicro.com>,
	Clément Léger <cleger@...osinc.com>,
	Anup Patel <apatel@...tanamicro.com>
Subject: [PATCH 0/2] RISC-V: turn sbi_ecall into a variadic macro

Padding the ecalls with zeros is not great for reasons in [1/2].
I could also redo the code to use sbi_ecall1~sbi_ecall8, and drop
sbi_ecall if you think that variadic macros are too evil.
[2/2] puts the new macro that into use, and I hopefully haven't deleted
any intentional trailing 0.

For a related issue, I hoped that the tracepoints in __sbi_ecall would
only add a nop or two, because __sbi_ecall without tracepoints looks
like this:
   0xffffffff80023ad0 <+0>:	addi	sp,sp,-32
   0xffffffff80023ad2 <+2>:	sd	s0,16(sp)
   0xffffffff80023ad4 <+4>:	sd	ra,24(sp)
   0xffffffff80023ad6 <+6>:	addi	s0,sp,32
   0xffffffff80023ad8 <+8>:	ecall
   0xffffffff80023adc <+12>:	ld	ra,24(sp)
   0xffffffff80023ade <+14>:	ld	s0,16(sp)
   0xffffffff80023ae0 <+16>:	addi	sp,sp,32
   0xffffffff80023ae2 <+18>:	ret

Maybe I am missing some kernel config, because __sbi_ecall currently
looks like this:
   0xffffffff80023e58 <+0>:	addi	sp,sp,-112
   0xffffffff80023e5a <+2>:	sd	s0,96(sp)
   0xffffffff80023e5c <+4>:	sd	s1,88(sp)
   0xffffffff80023e5e <+6>:	sd	s3,72(sp)
   0xffffffff80023e60 <+8>:	sd	s4,64(sp)
   0xffffffff80023e62 <+10>:	sd	s5,56(sp)
   0xffffffff80023e64 <+12>:	sd	s6,48(sp)
   0xffffffff80023e66 <+14>:	sd	s7,40(sp)
   0xffffffff80023e68 <+16>:	sd	s8,32(sp)
   0xffffffff80023e6a <+18>:	sd	s9,24(sp)
   0xffffffff80023e6c <+20>:	sd	ra,104(sp)
   0xffffffff80023e6e <+22>:	sd	s2,80(sp)
   0xffffffff80023e70 <+24>:	addi	s0,sp,112
   0xffffffff80023e72 <+26>:	mv	s9,a0
   0xffffffff80023e74 <+28>:	mv	s8,a1
   0xffffffff80023e76 <+30>:	mv	s7,a2
   0xffffffff80023e78 <+32>:	mv	s6,a3
   0xffffffff80023e7a <+34>:	mv	s5,a4
   0xffffffff80023e7c <+36>:	mv	s4,a5
   0xffffffff80023e7e <+38>:	mv	s3,a6
   0xffffffff80023e80 <+40>:	mv	s1,a7
   0xffffffff80023e82 <+42>:	nop
   0xffffffff80023e84 <+44>:	nop
   0xffffffff80023e88 <+48>:	mv	a0,s9
   0xffffffff80023e8a <+50>:	mv	a1,s8
   0xffffffff80023e8c <+52>:	mv	a2,s7
   0xffffffff80023e8e <+54>:	mv	a3,s6
   0xffffffff80023e90 <+56>:	mv	a4,s5
   0xffffffff80023e92 <+58>:	mv	a5,s4
   0xffffffff80023e94 <+60>:	mv	a6,s3
   0xffffffff80023e96 <+62>:	mv	a7,s1
   0xffffffff80023e98 <+64>:	ecall
   0xffffffff80023e9c <+68>:	mv	s3,a0
   0xffffffff80023e9e <+70>:	mv	s2,a1
   0xffffffff80023ea0 <+72>:	nop
   0xffffffff80023ea4 <+76>:	ld	ra,104(sp)
   0xffffffff80023ea6 <+78>:	ld	s0,96(sp)
   0xffffffff80023ea8 <+80>:	ld	s1,88(sp)
   0xffffffff80023eaa <+82>:	ld	s4,64(sp)
   0xffffffff80023eac <+84>:	ld	s5,56(sp)
   0xffffffff80023eae <+86>:	ld	s6,48(sp)
   0xffffffff80023eb0 <+88>:	ld	s7,40(sp)
   0xffffffff80023eb2 <+90>:	ld	s8,32(sp)
   0xffffffff80023eb4 <+92>:	ld	s9,24(sp)
   0xffffffff80023eb6 <+94>:	mv	a0,s3
   0xffffffff80023eb8 <+96>:	mv	a1,s2
   0xffffffff80023eba <+98>:	ld	s3,72(sp)
   0xffffffff80023ebc <+100>:	ld	s2,80(sp)
   0xffffffff80023ebe <+102>:	addi	sp,sp,112
   0xffffffff80023ec0 <+104>:	ret
   ...
   [The actual tracepoint handling goes up to +328.]

Radim Krčmář (2):
  RISC-V: sbi: turn sbi_ecall into variadic macro
  RISC-V: make use of variadic sbi_ecall

 arch/riscv/include/asm/kvm_nacl.h |  4 +--
 arch/riscv/include/asm/sbi.h      | 34 +++++++++++++++++-
 arch/riscv/kernel/cpu_ops_sbi.c   |  6 ++--
 arch/riscv/kernel/paravirt.c      |  2 +-
 arch/riscv/kernel/sbi.c           | 57 ++++++++++++++-----------------
 arch/riscv/kernel/sbi_ecall.c     |  2 +-
 arch/riscv/kernel/suspend.c       |  4 +--
 arch/riscv/kvm/nacl.c             |  7 ++--
 drivers/acpi/riscv/cppc.c         |  4 +--
 drivers/perf/riscv_pmu_sbi.c      | 48 +++++++++++++-------------
 10 files changed, 98 insertions(+), 70 deletions(-)

-- 
2.49.0