[PATCH RFC 2/3] riscv: Add Svukte extension support

[Max Hsu]

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.

This patch depends on patch "riscv: Per-thread envcfg CSR support" [1]

Link: https://lore.kernel.org/linux-riscv/20240814081126.956287-1-samuel.holland@sifive.com/ [1]

Reviewed-by: Samuel Holland <samuel.holland at sifive.com>
Signed-off-by: Max Hsu <max.hsu at sifive.com>
---
 arch/riscv/include/asm/csr.h   | 2 ++
 arch/riscv/include/asm/hwcap.h | 1 +
 arch/riscv/kernel/cpufeature.c | 4 ++++
 3 files changed, 7 insertions(+)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 25966995da04e090ff22a11e35be9bc24712f1a8..62b50667d539c50a0bfdadd1c6ab06cda948f6a8 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -122,6 +122,7 @@
 #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)
@@ -195,6 +196,7 @@
 /* xENVCFG flags */
 #define ENVCFG_STCE			(_AC(1, ULL) << 63)
 #define ENVCFG_PBMTE			(_AC(1, ULL) << 62)
+#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 5a0bd27fd11a6d3d3b573c19ebaeb89d23dd8535..87f88a3b3f967b27b50ed071eace631c50d07dc7 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -92,6 +92,7 @@
 #define RISCV_ISA_EXT_ZCF		83
 #define RISCV_ISA_EXT_ZCMOP		84
 #define RISCV_ISA_EXT_ZAWRS		85
+#define RISCV_ISA_EXT_SVUKTE		86
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index b3b9735cb19a8a155b2e6710223ffd0992b8133e..891225a605547b312ab81d81f76f9bbba6c1b658 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -384,6 +384,7 @@ 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),
 };
 
 const size_t riscv_isa_ext_count = ARRAY_SIZE(riscv_isa_ext);
@@ -925,6 +926,9 @@ 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