[PATCH RFC v4 2/3] riscv: Add Svukte extension support

[Max Hsu <max.hsu@xxxxxxxxxx>]

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@xxxxxxxxxx>
Reviewed-by: Deepak Gupta <debug@xxxxxxxxxxxx>
Signed-off-by: Max Hsu <max.hsu@xxxxxxxxxx>
---
 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 37bdea65bbd8a1a313cc7ba00b80fc5071b9809a..aeb62e9901452f8ded56961ab31dabbb2fd22cc6 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)
@@ -204,6 +205,7 @@
 #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 869da082252a460559c9beea3829cc90860d6e9a..811c34d64df88dff116abb52e05054715a474dc5 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -100,6 +100,7 @@
 #define RISCV_ISA_EXT_ZICCRSE		91
 #define RISCV_ISA_EXT_SVADE		92
 #define RISCV_ISA_EXT_SVADU		93
+#define RISCV_ISA_EXT_SVUKTE		94
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index c0916ed318c20e2e2f6354a3a4be1f4437f7f564..932774350de42ec9b66fd7d00efb478ad55856f4 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -402,6 +402,7 @@ 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),
 };
 
@@ -944,6 +945,10 @@ 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