[PATCH v8 1/5] RISC-V: Add Svade and Svadu Extensions Support

[Yong-Xuan Wang]

Svade and Svadu extensions represent two schemes for managing the PTE A/D
bits. When the PTE A/D bits need to be set, Svade extension intdicates
that a related page fault will be raised. In contrast, the Svadu extension
supports hardware updating of PTE A/D bits. Since the Svade extension is
mandatory and the Svadu extension is optional in RVA23 profile, by default
the M-mode firmware will enable the Svadu extension in the menvcfg CSR
when only Svadu is present in DT.

This patch detects Svade and Svadu extensions from DT and adds
arch_has_hw_pte_young() to enable optimization in MGLRU and
__wp_page_copy_user() when we have the PTE A/D bits hardware updating
support.

Co-developed-by: Jinyu Tang <tjytimi at 163.com>
Signed-off-by: Jinyu Tang <tjytimi at 163.com>
Signed-off-by: Yong-Xuan Wang <yongxuan.wang at sifive.com>
Reviewed-by: Andrew Jones <ajones at ventanamicro.com>
Reviewed-by: Alexandre Ghiti <alexghiti at rivosinc.com>
---
 arch/riscv/Kconfig               |  1 +
 arch/riscv/include/asm/csr.h     |  1 +
 arch/riscv/include/asm/hwcap.h   |  2 ++
 arch/riscv/include/asm/pgtable.h | 13 ++++++++++++-
 arch/riscv/kernel/cpufeature.c   | 12 ++++++++++++
 5 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 3ceec2ca84fa..014e512854a6 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -29,6 +29,7 @@ config RISCV
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_GIGANTIC_PAGE
+	select ARCH_HAS_HW_PTE_YOUNG
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_KERNEL_FPU_SUPPORT if 64BIT && FPU
 	select ARCH_HAS_MEMBARRIER_CALLBACKS
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 25966995da04..524cd4131c71 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -195,6 +195,7 @@
 /* xENVCFG flags */
 #define ENVCFG_STCE			(_AC(1, ULL) << 63)
 #define ENVCFG_PBMTE			(_AC(1, ULL) << 62)
+#define ENVCFG_ADUE			(_AC(1, ULL) << 61)
 #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 b18b202ca141..b0435fda09ae 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -93,6 +93,8 @@
 #define RISCV_ISA_EXT_ZCF		84
 #define RISCV_ISA_EXT_ZCMOP		85
 #define RISCV_ISA_EXT_ZAWRS		86
+#define RISCV_ISA_EXT_SVADE		87
+#define RISCV_ISA_EXT_SVADU		88
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 089f3c9f56a3..6f1a0534f319 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -120,6 +120,7 @@
 #include <asm/tlbflush.h>
 #include <linux/mm_types.h>
 #include <asm/compat.h>
+#include <asm/cpufeature.h>
 
 #define __page_val_to_pfn(_val)  (((_val) & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT)
 
@@ -288,7 +289,6 @@ static inline pte_t pud_pte(pud_t pud)
 }
 
 #ifdef CONFIG_RISCV_ISA_SVNAPOT
-#include <asm/cpufeature.h>
 
 static __always_inline bool has_svnapot(void)
 {
@@ -649,6 +649,17 @@ static inline pgprot_t pgprot_writecombine(pgprot_t _prot)
 	return __pgprot(prot);
 }
 
+/*
+ * Both Svade and Svadu control the hardware behavior when the PTE A/D bits need to be set. By
+ * default the M-mode firmware enables the hardware updating scheme when only Svadu is present in
+ * DT.
+ */
+#define arch_has_hw_pte_young arch_has_hw_pte_young
+static inline bool arch_has_hw_pte_young(void)
+{
+	return riscv_has_extension_unlikely(RISCV_ISA_EXT_SVADU);
+}
+
 /*
  * THP functions
  */
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 0366dc3baf33..2a9cdfae21c6 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -156,6 +156,16 @@ static int riscv_ext_zcf_validate(const struct riscv_isa_ext_data *data,
 	return -EPROBE_DEFER;
 }
 
+static int riscv_ext_svadu_validate(const struct riscv_isa_ext_data *data,
+				    const unsigned long *isa_bitmap)
+{
+	/* SVADE has already been detected, use SVADE only */
+	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_SVADE))
+		return -EOPNOTSUPP;
+
+	return 0;
+}
+
 static const unsigned int riscv_zk_bundled_exts[] = {
 	RISCV_ISA_EXT_ZBKB,
 	RISCV_ISA_EXT_ZBKC,
@@ -402,6 +412,8 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(ssaia, RISCV_ISA_EXT_SSAIA),
 	__RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF),
 	__RISCV_ISA_EXT_DATA(sstc, RISCV_ISA_EXT_SSTC),
+	__RISCV_ISA_EXT_DATA(svade, RISCV_ISA_EXT_SVADE),
+	__RISCV_ISA_EXT_DATA_VALIDATE(svadu, RISCV_ISA_EXT_SVADU, riscv_ext_svadu_validate),
 	__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),
-- 
2.17.1