linux-kernel - [PATCH RFC v3 2/3] riscv: Add Svukte extension support

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Message-Id: <20241120-dev-maxh-svukte-v3-v3-2-1e533d41ae15@sifive.com>
Date: Wed, 20 Nov 2024 22:09:33 +0800
From: Max Hsu <max.hsu@...ive.com>
To: Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>
Cc: Palmer Dabbelt <palmer@...ive.com>, linux-riscv@...ts.infradead.org, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
 Max Hsu <max.hsu@...ive.com>, Samuel Holland <samuel.holland@...ive.com>, 
 Deepak Gupta <debug@...osinc.com>
Subject: [PATCH RFC v3 2/3] riscv: Add Svukte extension support

Svukte extension introduce senvcfg.UKTE, hstatus.HUKTE.

This patch add CSR bit definition, and detects if Svukte ISA extension
is available, cpufeature will set the correspond bit field so the
svukte-qualified memory accesses are protected in a manner that is
timing-independent of the faulting virtual address.

Since hstatus.HU is not enabled by linux, enabling hstatus.HUKTE will
not be affective.

Reviewed-by: Samuel Holland <samuel.holland@...ive.com>
Reviewed-by: Deepak Gupta <debug@...osinc.com>
Signed-off-by: Max Hsu <max.hsu@...ive.com>
---
 arch/riscv/include/asm/csr.h   | 2 ++
 arch/riscv/include/asm/hwcap.h | 1 +
 arch/riscv/kernel/cpufeature.c | 5 +++++
 3 files changed, 8 insertions(+)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index fe5d4eb9adea1d4e3065a4d6e2ff361a52aecc44..67ff78f7e480bcbfef04e58191ef85d5434f427e 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -126,6 +126,7 @@
 #define HSTATUS_VSXL		_AC(0x300000000, UL)
 #define HSTATUS_VSXL_SHIFT	32
 #endif
+#define HSTATUS_HUKTE		_AC(0x01000000, UL)
 #define HSTATUS_VTSR		_AC(0x00400000, UL)
 #define HSTATUS_VTW		_AC(0x00200000, UL)
 #define HSTATUS_VTVM		_AC(0x00100000, UL)
@@ -203,6 +204,7 @@
 #define ENVCFG_PMM_PMLEN_0		(_AC(0x0, ULL) << 32)
 #define ENVCFG_PMM_PMLEN_7		(_AC(0x2, ULL) << 32)
 #define ENVCFG_PMM_PMLEN_16		(_AC(0x3, ULL) << 32)
+#define ENVCFG_UKTE			(_AC(1, UL) << 8)
 #define ENVCFG_CBZE			(_AC(1, UL) << 7)
 #define ENVCFG_CBCFE			(_AC(1, UL) << 6)
 #define ENVCFG_CBIE_SHIFT		4
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 08d2a5697466d07fe2319a2423f04657177db37f..98488d8ebf528ff5cd494ab753d91b77accd2488 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -98,6 +98,7 @@
 #define RISCV_ISA_EXT_SSNPM		89
 #define RISCV_ISA_EXT_ZABHA		90
 #define RISCV_ISA_EXT_ZICCRSE		91
+#define RISCV_ISA_EXT_SVUKTE		92
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index eb904ca64ad03565c6d521350f5e6b4c5cb9c6d9..a38e40477f0123eb7e80b096a38e0f956c9d4bc0 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -389,6 +389,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
 	__RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
 	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
+	__RISCV_ISA_EXT_SUPERSET(svukte, RISCV_ISA_EXT_SVUKTE, riscv_xlinuxenvcfg_exts),
 	__RISCV_ISA_EXT_DATA(svvptc, RISCV_ISA_EXT_SVVPTC),
 };
 
@@ -931,6 +932,10 @@ void __init riscv_user_isa_enable(void)
 		current->thread.envcfg |= ENVCFG_CBZE;
 	else if (any_cpu_has_zicboz)
 		pr_warn("Zicboz disabled as it is unavailable on some harts\n");
+
+	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SVUKTE))
+		current->thread.envcfg |= ENVCFG_UKTE;
+
 }
 
 #ifdef CONFIG_RISCV_ALTERNATIVE

-- 
2.43.2