linux-kernel - [PATCH v5 09/21] RISC-V: Add Ssccfg/Smcdeleg ISA extension definition and parsing

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Message-Id: <20250327-counter_delegation-v5-9-1ee538468d1b@rivosinc.com>
Date: Thu, 27 Mar 2025 12:35:50 -0700
From: Atish Patra <atishp@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Anup Patel <anup@...infault.org>, 
 Atish Patra <atishp@...shpatra.org>, Will Deacon <will@...nel.org>, 
 Mark Rutland <mark.rutland@....com>, Peter Zijlstra <peterz@...radead.org>, 
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Namhyung Kim <namhyung@...nel.org>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>, 
 Adrian Hunter <adrian.hunter@...el.com>, weilin.wang@...el.com
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Conor Dooley <conor@...nel.org>, devicetree@...r.kernel.org, 
 kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
 linux-arm-kernel@...ts.infradead.org, linux-perf-users@...r.kernel.org, 
 Atish Patra <atishp@...osinc.com>
Subject: [PATCH v5 09/21] RISC-V: Add Ssccfg/Smcdeleg ISA extension
 definition and parsing

Smcdeleg extension allows the M-mode to delegate selected counters
to S-mode so that it can access those counters and correpsonding
hpmevent CSRs without M-mode.

Ssccfg (‘Ss’ for Privileged architecture and Supervisor-level
extension, ‘ccfg’ for Counter Configuration) provides access to
delegated counters and new supervisor-level state.

This patch just enables these definitions and enable parsing.

Signed-off-by: Atish Patra <atishp@...osinc.com>
---
 arch/riscv/include/asm/hwcap.h |  2 ++
 arch/riscv/kernel/cpufeature.c | 24 ++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index b4eddcb57842..fa5e01bcb990 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -103,6 +103,8 @@
 #define RISCV_ISA_EXT_SSCSRIND		94
 #define RISCV_ISA_EXT_SMCSRIND		95
 #define RISCV_ISA_EXT_SMCNTRPMF         96
+#define RISCV_ISA_EXT_SSCCFG            97
+#define RISCV_ISA_EXT_SMCDELEG          98
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index e3e40cfe7967..f72552adb257 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -150,6 +150,27 @@ static int riscv_ext_svadu_validate(const struct riscv_isa_ext_data *data,
 	return 0;
 }
 
+static int riscv_ext_smcdeleg_validate(const struct riscv_isa_ext_data *data,
+				       const unsigned long *isa_bitmap)
+{
+	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_SSCSRIND) &&
+	    __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZIHPM) &&
+	    __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZICNTR))
+		return 0;
+
+	return -EPROBE_DEFER;
+}
+
+static int riscv_ext_ssccfg_validate(const struct riscv_isa_ext_data *data,
+				     const unsigned long *isa_bitmap)
+{
+	if (!riscv_ext_smcdeleg_validate(data, isa_bitmap) &&
+	    __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_SMCDELEG))
+		return 0;
+
+	return -EPROBE_DEFER;
+}
+
 static const unsigned int riscv_zk_bundled_exts[] = {
 	RISCV_ISA_EXT_ZBKB,
 	RISCV_ISA_EXT_ZBKC,
@@ -394,12 +415,15 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_BUNDLE(zvksg, riscv_zvksg_bundled_exts),
 	__RISCV_ISA_EXT_DATA(zvkt, RISCV_ISA_EXT_ZVKT),
 	__RISCV_ISA_EXT_DATA(smaia, RISCV_ISA_EXT_SMAIA),
+	__RISCV_ISA_EXT_DATA_VALIDATE(smcdeleg, RISCV_ISA_EXT_SMCDELEG,
+				      riscv_ext_smcdeleg_validate),
 	__RISCV_ISA_EXT_DATA(smcntrpmf, RISCV_ISA_EXT_SMCNTRPMF),
 	__RISCV_ISA_EXT_DATA(smcsrind, RISCV_ISA_EXT_SMCSRIND),
 	__RISCV_ISA_EXT_DATA(smmpm, RISCV_ISA_EXT_SMMPM),
 	__RISCV_ISA_EXT_SUPERSET(smnpm, RISCV_ISA_EXT_SMNPM, riscv_xlinuxenvcfg_exts),
 	__RISCV_ISA_EXT_DATA(smstateen, RISCV_ISA_EXT_SMSTATEEN),
 	__RISCV_ISA_EXT_DATA(ssaia, RISCV_ISA_EXT_SSAIA),
+	__RISCV_ISA_EXT_DATA_VALIDATE(ssccfg, RISCV_ISA_EXT_SSCCFG, riscv_ext_ssccfg_validate),
 	__RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF),
 	__RISCV_ISA_EXT_DATA(sscsrind, RISCV_ISA_EXT_SSCSRIND),
 	__RISCV_ISA_EXT_SUPERSET(ssnpm, RISCV_ISA_EXT_SSNPM, riscv_xlinuxenvcfg_exts),

-- 
2.43.0