[PATCH v5 1/4] 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@xxxxxxx>
Signed-off-by: Jinyu Tang <tjytimi@xxxxxxx>
Signed-off-by: Yong-Xuan Wang <yongxuan.wang@xxxxxxxxxx>
---
 arch/riscv/Kconfig               |  1 +
 arch/riscv/include/asm/csr.h     |  1 +
 arch/riscv/include/asm/hwcap.h   |  2 ++
 arch/riscv/include/asm/pgtable.h | 14 +++++++++++++-
 arch/riscv/kernel/cpufeature.c   |  2 ++
 5 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index b94176e25be1..dbfe2be99bf9 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -36,6 +36,7 @@ config RISCV
 	select ARCH_HAS_PMEM_API
 	select ARCH_HAS_PREPARE_SYNC_CORE_CMD
 	select ARCH_HAS_PTE_SPECIAL
+	select ARCH_HAS_HW_PTE_YOUNG
 	select ARCH_HAS_SET_DIRECT_MAP if MMU
 	select ARCH_HAS_SET_MEMORY if MMU
 	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
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 e17d0078a651..35d7aa49785d 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -81,6 +81,8 @@
 #define RISCV_ISA_EXT_ZTSO		72
 #define RISCV_ISA_EXT_ZACAS		73
 #define RISCV_ISA_EXT_XANDESPMU		74
+#define RISCV_ISA_EXT_SVADE             75
+#define RISCV_ISA_EXT_SVADU		76
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index aad8b8ca51f1..7287ea4a6160 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)
 {
@@ -624,6 +624,18 @@ 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) &&
+	       !riscv_has_extension_likely(RISCV_ISA_EXT_SVADE);
+}
+
 /*
  * THP functions
  */
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 5ef48cb20ee1..58565798cea0 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -301,6 +301,8 @@ 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(svadu, RISCV_ISA_EXT_SVADU),
 	__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