[Qemu-devel] [PATCH for 4.1] target/riscv: More accurate handling of `sip` CSR

[Jonathan Behrens]

According to the spec, "All bits besides SSIP, USIP, and UEIP in the sip
register are read-only." Further, if an interrupt is not delegated to mode
x,
then "the corresponding bits in xip [...] should appear to be hardwired to
zero. This patch implements both of those requirements.

Signed-off-by: Jonathan Behrens <address@hidden>
---
 target/riscv/csr.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 1ec1222da1..fff7d834e8 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -246,6 +246,7 @@ static const target_ulong sstatus_v1_9_mask =
SSTATUS_SIE | SSTATUS_SPIE |
 static const target_ulong sstatus_v1_10_mask = SSTATUS_SIE | SSTATUS_SPIE |
     SSTATUS_UIE | SSTATUS_UPIE | SSTATUS_SPP | SSTATUS_FS | SSTATUS_XS |
     SSTATUS_SUM | SSTATUS_MXR | SSTATUS_SD;
+static const target_ulong sip_writable_mask = SIP_SSIP | MIP_USIP |
MIP_UEIP;

 #if defined(TARGET_RISCV32)
 static const char valid_vm_1_09[16] = {
@@ -694,8 +695,10 @@ static int write_sbadaddr(CPURISCVState *env, int
csrno, target_ulong val)
 static int rmw_sip(CPURISCVState *env, int csrno, target_ulong *ret_value,
                    target_ulong new_value, target_ulong write_mask)
 {
-    return rmw_mip(env, CSR_MSTATUS, ret_value, new_value,
-                   write_mask & env->mideleg);
+    int ret = rmw_mip(env, CSR_MSTATUS, ret_value, new_value,
+                      write_mask & env->mideleg & sip_writable_mask);
+    *ret_value &= env->mideleg;
+    return ret;
 }

 /* Supervisor Protection and Translation */
-- 
2.20.1