[RFC PATCH v4 1/5] RISC-V: Detect and Enable Svadu Extension Support

[Yong-Xuan Wang]

Svadu is a RISC-V extension for hardware updating of PTE A/D bits.

In this patch we detect Svadu extension support from DTB and enable it
with SBI FWFT extension. Also we add arch_has_hw_pte_young() to enable
optimization in MGLRU and __wp_page_copy_user() if Svadu extension is
available.

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: Conor Dooley <conor.dooley at microchip.com>
Reviewed-by: Andrew Jones <ajones at ventanamicro.com>
---
 arch/riscv/Kconfig               |  1 +
 arch/riscv/include/asm/csr.h     |  1 +
 arch/riscv/include/asm/hwcap.h   |  1 +
 arch/riscv/include/asm/pgtable.h |  8 +++++++-
 arch/riscv/kernel/cpufeature.c   | 11 +++++++++++
 5 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index be09c8836d56..30fa558ee284 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -34,6 +34,7 @@ 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 2468c55933cd..2ac270ad4acd 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -194,6 +194,7 @@
 /* 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..8d539e3f4e11 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -81,6 +81,7 @@
 #define RISCV_ISA_EXT_ZTSO		72
 #define RISCV_ISA_EXT_ZACAS		73
 #define RISCV_ISA_EXT_XANDESPMU		74
+#define RISCV_ISA_EXT_SVADU		75
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 9f8ea0e33eb1..1f1b326ccf63 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -117,6 +117,7 @@
 #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)
 
@@ -285,7 +286,6 @@ 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)
 {
@@ -621,6 +621,12 @@ static inline pgprot_t pgprot_writecombine(pgprot_t _prot)
 	return __pgprot(prot);
 }
 
+#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 3ed2359eae35..b023908c5932 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -93,6 +93,16 @@ static bool riscv_isa_extension_check(int id)
 			return false;
 		}
 		return true;
+	case RISCV_ISA_EXT_SVADU:
+		if (sbi_probe_extension(SBI_EXT_FWFT) > 0) {
+			struct sbiret ret;
+
+			ret = sbi_ecall(SBI_EXT_FWFT, SBI_EXT_FWFT_SET, SBI_FWFT_PTE_AD_HW_UPDATING,
+					1, 0, 0, 0, 0);
+
+			return ret.error == SBI_SUCCESS;
+		}
+		return false;
 	case RISCV_ISA_EXT_INVALID:
 		return false;
 	}
@@ -301,6 +311,7 @@ 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_SUPERSET(svadu, RISCV_ISA_EXT_SVADU, riscv_xlinuxenvcfg_exts),
 	__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