[RFC 3/3] lib: sbi: enable seed access in S-mode

[Heinrich Schuchardt]

If ISA extension Zkr is available, set

    mseccfg.sseed=1
    mseccfg.useed=0

This enables access to the seed CSR in S-mode but not in U-mode.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
---
 lib/sbi/sbi_hart.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 569596f..5a3e8ee 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -530,6 +530,15 @@ int sbi_hart_unmap_saddr(void)
 	return pmp_disable(SBI_SMEPMP_RESV_ENTRY);
 }
 
+static void sbi_hart_zkr_configure(struct sbi_scratch *scratch)
+{
+	unsigned long mseccfg_val = csr_read(CSR_MSECCFG);
+
+	mseccfg_val |= MSECCFG_SSEED;
+	mseccfg_val &= ~MSECCFG_USEED;
+	csr_set(CSR_MSECCFG, mseccfg_val);
+}
+
 int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
 {
 	int rc;
@@ -551,6 +560,9 @@ int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
 		rc = sbi_hart_oldpmp_configure(scratch, pmp_count,
 						pmp_gran_log2, pmp_addr_max);
 
+	if (sbi_hart_has_extension(scratch, SBI_HART_EXT_ZKR))
+		sbi_hart_zkr_configure(scratch);
+
 	/*
 	 * As per section 3.7.2 of privileged specification v1.12,
 	 * virtual address translations can be speculatively performed
-- 
2.40.1