linux-kernel - [PATCH v2 0/2] RISC-V: turn sbi

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Message-ID: <20250619190315.2603194-1-rkrcmar@ventanamicro.com>
Date: Thu, 19 Jun 2025 21:03:12 +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>,
	Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
	David Laight <david.laight.linux@...il.com>
Subject: [PATCH v2 0/2] RISC-V: turn sbi_ecall into a variadic macro

v2 has a completely rewritten [1/2], and fixes some missed trailing
zeroes in [2/2].  The fixes in [2/2] are important for v2, because
sbi_ecall doesn't fill the registers with zeroes anymore.

In the future, I think it would be nice to have a wrapper function for
each sbi_ecall, to make the code less error-prone.

GCC isn't doing a good job with sbi_ecall.  v2 is a bit better than v1,
because some ecall registers are not used in the assembly, but nowhere
near good enough...
The compiler doesn't consider static key'd tracepoint branches to be
special, and prepares for trace function calls outside of the unlikely
path.  Instead of a single "nop" for a tracepoint, the non-trace path
also does a lot of pointless register save/restore.
I'm looking for help with this issue in [3/2].

v2:
 * use linux/args.h [Thomas] [1/2]
 * completely rewrite [1/2]
 * remove __sbi_ecall [1/2]
 * add some missed trailing 0 in pmu [David] [2/2]
 * adapt to the new sbi_ecall that doesn't allow a single argument [2/2]

v1: https://lore.kernel.org/linux-riscv/20250612145754.2126147-2-rkrcmar@ventanamicro.com/T/#m1d441ab3de3e6d6b3b8d120b923f2e2081918a98

Radim Krčmář (3):
  RISC-V: sbi: turn sbi_ecall into variadic macro
  RISC-V: make use of variadic sbi_ecall
  RISC-V: sbi: remove sbi_ecall tracepoints

 arch/riscv/include/asm/kvm_nacl.h |  4 +--
 arch/riscv/include/asm/sbi.h      | 55 +++++++++++++++++++++++++----
 arch/riscv/include/asm/trace.h    | 36 -------------------
 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     | 34 +-----------------
 arch/riscv/kernel/suspend.c       |  4 +--
 arch/riscv/kvm/nacl.c             |  7 ++--
 drivers/acpi/riscv/cppc.c         |  4 +--
 drivers/perf/riscv_pmu_sbi.c      | 49 +++++++++++++-------------
 11 files changed, 115 insertions(+), 143 deletions(-)

-- 
2.49.0