[PATCH v4 1/2] lib: sbi: Detect PMP granularity and number of address bits

[Atish Patra]

As per RISC-V privilege specification, a platform may choose to implement
a coarser granularity scheme for PMP addresses. In that case, we shouldn't
allow any pmp region size smaller than the platform supports. A platform
may not also implement all the bits for a PMP address specified in the priv
specification.

The pmp range granularity and address bits should be detected dynamically
before detecing PMP regions. Any pmp modification request beyond these detected
value must not succeed.

Signed-off-by: Atish Patra <atish.patra at wdc.com>
---
 include/sbi/sbi_hart.h |  2 ++
 lib/sbi/sbi_hart.c     | 62 +++++++++++++++++++++++++++++++++++++++---
 2 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index 3ac150036c79..ec9e30f913ce 100644
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -39,6 +39,8 @@ unsigned int sbi_hart_mhpm_count(struct sbi_scratch *scratch);
 void sbi_hart_delegation_dump(struct sbi_scratch *scratch,
 			      const char *prefix, const char *suffix);
 unsigned int sbi_hart_pmp_count(struct sbi_scratch *scratch);
+unsigned long sbi_hart_pmp_granularity(struct sbi_scratch *scratch);
+unsigned int sbi_hart_pmp_addrbits(struct sbi_scratch *scratch);
 int sbi_hart_pmp_configure(struct sbi_scratch *scratch);
 bool sbi_hart_has_feature(struct sbi_scratch *scratch, unsigned long feature);
 void sbi_hart_get_features_str(struct sbi_scratch *scratch,
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 8ded82841d82..1e3a759229ca 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -30,6 +30,8 @@ void (*sbi_hart_expected_trap)(void) = &__sbi_expected_trap;
 struct hart_features {
 	unsigned long features;
 	unsigned int pmp_count;
+	unsigned int pmp_addr_bits;
+	unsigned long pmp_gran;
 	unsigned int mhpm_count;
 };
 static unsigned long hart_features_offset;
@@ -159,16 +161,37 @@ unsigned int sbi_hart_pmp_count(struct sbi_scratch *scratch)
 	return hfeatures->pmp_count;
 }
 
+unsigned long sbi_hart_pmp_granularity(struct sbi_scratch *scratch)
+{
+	struct hart_features *hfeatures =
+			sbi_scratch_offset_ptr(scratch, hart_features_offset);
+
+	return hfeatures->pmp_gran;
+}
+
+unsigned int sbi_hart_pmp_addrbits(struct sbi_scratch *scratch)
+{
+	struct hart_features *hfeatures =
+			sbi_scratch_offset_ptr(scratch, hart_features_offset);
+
+	return hfeatures->pmp_addr_bits;
+}
+
 int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
 {
 	struct sbi_domain_memregion *reg;
 	struct sbi_domain *dom = sbi_domain_thishart_ptr();
-	unsigned int pmp_idx = 0, pmp_flags;
+	unsigned int pmp_idx = 0, pmp_flags, pmp_bits, pmp_gran_log2;
 	unsigned int pmp_count = sbi_hart_pmp_count(scratch);
+	unsigned long pmp_addr = 0, pmp_addr_max = 0;
 
 	if (!pmp_count)
 		return 0;
 
+	pmp_gran_log2 = log2roundup(sbi_hart_pmp_granularity(scratch));
+	pmp_bits = sbi_hart_pmp_addrbits(scratch) - 1;
+	pmp_addr_max = (1UL << pmp_bits) | ((1UL << pmp_bits) - 1);
+
 	sbi_domain_for_each_memregion(dom, reg) {
 		if (pmp_count <= pmp_idx)
 			break;
@@ -183,7 +206,14 @@ int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
 		if (reg->flags & SBI_DOMAIN_MEMREGION_MMODE)
 			pmp_flags |= PMP_L;
 
-		pmp_set(pmp_idx++, pmp_flags, reg->base, reg->order);
+		pmp_addr =  reg->base >> PMP_SHIFT;
+		if (pmp_gran_log2 <= reg->order && pmp_addr < pmp_addr_max)
+			pmp_set(pmp_idx++, pmp_flags, reg->base, reg->order);
+		else {
+			sbi_printf("Can not configure pmp for domain %s", dom->name);
+			sbi_printf("because memory region address %lx or size %lx is not in range\n",
+				    reg->base, reg->order);
+		}
 	}
 
 	return 0;
@@ -282,6 +312,21 @@ done:
 		sbi_strncpy(features_str, "none", nfstr);
 }
 
+static unsigned long hart_pmp_get_allowed_addr(void)
+{
+	unsigned long val = 0;
+	struct sbi_trap_info trap = {0};
+
+	csr_write_allowed(CSR_PMPADDR0, (ulong)&trap, PMP_ADDR_MASK);			\
+	if (!trap.cause) {
+		val = csr_read_allowed(CSR_PMPADDR0, (ulong)&trap);
+		if (trap.cause)
+			val = 0;
+	}
+
+	return val;
+}
+
 static void hart_detect_features(struct sbi_scratch *scratch)
 {
 	struct sbi_trap_info trap = {0};
@@ -332,8 +377,17 @@ static void hart_detect_features(struct sbi_scratch *scratch)
 	__check_csr_32(__csr + 0, __rdonly, __wrval, __field, __skip)	\
 	__check_csr_32(__csr + 32, __rdonly, __wrval, __field, __skip)
 
-	/* Detect number of PMP regions */
-	__check_csr_64(CSR_PMPADDR0, 0, 1UL, pmp_count, __pmp_skip);
+	/**
+	 * Detect the allowed address bits & granularity. At least PMPADDR0
+	 * should be implemented.
+	 */
+	val = hart_pmp_get_allowed_addr();
+	if (val) {
+		hfeatures->pmp_gran =  1 << (__ffs(val) + 2);
+		hfeatures->pmp_addr_bits = __fls(val) + 1;
+		/* Detect number of PMP regions. At least PMPADDR0 should be implemented*/
+		__check_csr_64(CSR_PMPADDR0, 0, val, pmp_count, __pmp_skip);
+	}
 __pmp_skip:
 
 	/* Detect number of MHPM counters */
-- 
2.25.1