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

Yong-Xuan Wang
2024-07-26T08:49:47Z

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@163.com>
Signed-off-by: Jinyu Tang <tjytimi@163.com>
Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alexandre Ghiti <alexghiti@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