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

From: Max Hsu
Date: Fri Dec 13 2024 - 06:35:08 EST


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