[PATCH] lib: sbi: fwft: add support for SBI_FWFT_POINTER_MASKING_PMLEN

[Samuel Holland]

Add support for controlling the pointer masking mode on harts which
support the Smnpm extension. This extension can only exist on harts
where XLEN >= 64 bits. This implementation selects the mode with the
smallest PMLEN that satisfies the caller's requested lower bound.

Signed-off-by: Samuel Holland <samuel.holland at sifive.com>
---
This patch implements the API I originally suggested while the FWFT
extension was a draft and also submitted here:
https://github.com/riscv-non-isa/riscv-sbi-doc/pull/161

 include/sbi/riscv_encoding.h      |  4 ++
 include/sbi/sbi_ecall_interface.h |  3 +-
 include/sbi/sbi_hart.h            |  2 +
 lib/sbi/sbi_fwft.c                | 67 +++++++++++++++++++++++++++++++
 lib/sbi/sbi_hart.c                |  1 +
 5 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/include/sbi/riscv_encoding.h b/include/sbi/riscv_encoding.h
index 2ed05f24..beb874af 100644
--- a/include/sbi/riscv_encoding.h
+++ b/include/sbi/riscv_encoding.h
@@ -213,6 +213,10 @@
 #define ENVCFG_PBMTE			(_ULL(1) << 62)
 #define ENVCFG_ADUE			(_ULL(1) << 61)
 #define ENVCFG_CDE			(_ULL(1) << 60)
+#define ENVCFG_PMM			(_ULL(0x3) << 32)
+#define ENVCFG_PMM_PMLEN_0		(_ULL(0x0) << 32)
+#define ENVCFG_PMM_PMLEN_7		(_ULL(0x2) << 32)
+#define ENVCFG_PMM_PMLEN_16		(_ULL(0x3) << 32)
 #define ENVCFG_CBZE			(_UL(1) << 7)
 #define ENVCFG_CBCFE			(_UL(1) << 6)
 #define ENVCFG_CBIE_SHIFT		4
diff --git a/include/sbi/sbi_ecall_interface.h b/include/sbi/sbi_ecall_interface.h
index e9a81677..2958b418 100644
--- a/include/sbi/sbi_ecall_interface.h
+++ b/include/sbi/sbi_ecall_interface.h
@@ -128,7 +128,8 @@ enum sbi_fwft_feature_t {
 	SBI_FWFT_SHADOW_STACK			= 0x2,
 	SBI_FWFT_DOUBLE_TRAP			= 0x3,
 	SBI_FWFT_PTE_AD_HW_UPDATING		= 0x4,
-	SBI_FWFT_LOCAL_RESERVED_START		= 0x5,
+	SBI_FWFT_POINTER_MASKING_PMLEN		= 0x5,
+	SBI_FWFT_LOCAL_RESERVED_START		= 0x6,
 	SBI_FWFT_LOCAL_RESERVED_END		= 0x3fffffff,
 	SBI_FWFT_LOCAL_PLATFORM_START		= 0x40000000,
 	SBI_FWFT_LOCAL_PLATFORM_END		= 0x7fffffff,
diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index 81ec061d..32545f41 100644
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -67,6 +67,8 @@ enum sbi_hart_extensions {
 	SBI_HART_EXT_SVADE,
 	/** Hart has Svadu extension */
 	SBI_HART_EXT_SVADU,
+	/** Hart has Smnpm extension */
+	SBI_HART_EXT_SMNPM,
 
 	/** Maximum index of Hart extension */
 	SBI_HART_EXT_MAX,
diff --git a/lib/sbi/sbi_fwft.c b/lib/sbi/sbi_fwft.c
index ef881ef5..c5803300 100644
--- a/lib/sbi/sbi_fwft.c
+++ b/lib/sbi/sbi_fwft.c
@@ -59,6 +59,7 @@ static const unsigned long fwft_defined_features[] = {
 	SBI_FWFT_SHADOW_STACK,
 	SBI_FWFT_DOUBLE_TRAP,
 	SBI_FWFT_PTE_AD_HW_UPDATING,
+	SBI_FWFT_POINTER_MASKING_PMLEN,
 };
 
 static bool fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
@@ -145,6 +146,64 @@ static int fwft_get_adue(struct fwft_config *conf, unsigned long *value)
 	return SBI_OK;
 }
 
+#if __riscv_xlen > 32
+static int fwft_pmlen_supported(struct fwft_config *conf)
+{
+	if (!sbi_hart_has_extension(sbi_scratch_thishart_ptr(),
+				    SBI_HART_EXT_SMNPM))
+		return SBI_ENOTSUPP;
+
+	return SBI_OK;
+}
+
+static bool fwft_try_to_set_pmm(unsigned long pmm)
+{
+	csr_set(CSR_MENVCFG, pmm);
+	return (csr_read(CSR_MENVCFG) & ENVCFG_PMM) == pmm;
+}
+
+static int fwft_set_pmlen(struct fwft_config *conf, unsigned long value)
+{
+	unsigned long prev;
+
+	if (value > 16)
+		return SBI_EINVAL;
+
+	prev = csr_read_clear(CSR_MENVCFG, ENVCFG_PMM);
+	if (value == 0)
+		return SBI_OK;
+	if (value <= 7) {
+		if (fwft_try_to_set_pmm(ENVCFG_PMM_PMLEN_7))
+			return SBI_OK;
+		csr_clear(CSR_MENVCFG, ENVCFG_PMM);
+	}
+	if (fwft_try_to_set_pmm(ENVCFG_PMM_PMLEN_16))
+		return SBI_OK;
+	csr_write(CSR_MENVCFG, prev);
+
+	return SBI_EINVAL;
+}
+
+static int fwft_get_pmlen(struct fwft_config *conf, unsigned long *value)
+{
+	switch (csr_read(CSR_MENVCFG) & ENVCFG_PMM) {
+	case ENVCFG_PMM_PMLEN_0:
+		*value = 0;
+		break;
+	case ENVCFG_PMM_PMLEN_7:
+		*value = 7;
+		break;
+	case ENVCFG_PMM_PMLEN_16:
+		*value = 16;
+		break;
+	default:
+		return SBI_EFAIL;
+	}
+
+	return SBI_OK;
+}
+#endif
+
 static struct fwft_config* get_feature_config(enum sbi_fwft_feature_t feature)
 {
 	int i;
@@ -236,6 +295,14 @@ static const struct fwft_feature features[] =
 		.set = fwft_set_adue,
 		.get = fwft_get_adue,
 	},
+#if __riscv_xlen > 32
+	{
+		.id = SBI_FWFT_POINTER_MASKING_PMLEN,
+		.supported = fwft_pmlen_supported,
+		.set = fwft_set_pmlen,
+		.get = fwft_get_pmlen,
+	},
+#endif
 };
 
 int sbi_fwft_init(struct sbi_scratch *scratch, bool cold_boot)
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index c3667019..8c5bcf85 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -680,6 +680,7 @@ const struct sbi_hart_ext_data sbi_hart_ext[] = {
 	__SBI_HART_EXT_DATA(ssccfg, SBI_HART_EXT_SSCCFG),
 	__SBI_HART_EXT_DATA(svade, SBI_HART_EXT_SVADE),
 	__SBI_HART_EXT_DATA(svadu, SBI_HART_EXT_SVADU),
+	__SBI_HART_EXT_DATA(smnpm, SBI_HART_EXT_SMNPM),
 };
 
 _Static_assert(SBI_HART_EXT_MAX == array_size(sbi_hart_ext),
-- 
2.45.1