Correctly instantiate PLIC contexts for mixed-hart targets

This commit started as an attempt to make the PLIC tolerant of
discontiguous hart IDs, but it turns out it was already most of
the way there: PLIC contexts can still be dense even if the hart
IDs are not.

Nevertheless, I wanted to avoid passing the procs vector directly to
the plic_t constructor.  In removing it, I realized I could also get
rid of the smode parameter by querying whether each hart has S-mode.
This is also more correct; previously, we were instantiating the PLIC
as though all harts had S-mode, regardless of whether they actually did.

3 files changed, 20 insertions, 11 deletions

diff --git a/riscv/devices.h b/riscv/devices.h
index 53db96a..6facaa3 100644
--- a/riscv/devices.h
+++ b/riscv/devices.h
@@ -12,6 +12,7 @@
 #include <utility>
 
 class processor_t;
+class sim_t;
 
 class bus_t : public abstract_device_t {
  public:
@@ -91,7 +92,7 @@ struct plic_context_t {
 
 class plic_t : public abstract_device_t, public abstract_interrupt_controller_t {
  public:
-  plic_t(std::vector<processor_t*>&, bool smode, uint32_t ndev);
+  plic_t(sim_t*, uint32_t ndev);
   bool load(reg_t addr, size_t len, uint8_t* bytes);
   bool store(reg_t addr, size_t len, const uint8_t* bytes);
   void set_interrupt_level(uint32_t id, int lvl);
diff --git a/riscv/plic.cc b/riscv/plic.cc
index e070c9e..64041b7 100644
--- a/riscv/plic.cc
+++ b/riscv/plic.cc
@@ -1,6 +1,7 @@
 #include <sys/time.h>
 #include "devices.h"
 #include "processor.h"
+#include "sim.h"
 
 #define PLIC_MAX_CONTEXTS 15872
 
@@ -66,11 +67,8 @@
 
 #define REG_SIZE                0x1000000
 
-plic_t::plic_t(std::vector<processor_t*>& procs, bool smode, uint32_t ndev)
-  : contexts(procs.size() * (smode ? 2 : 1))
+plic_t::plic_t(sim_t* sim, uint32_t ndev)
 {
-  size_t contexts_per_hart = smode ? 2 : 1;
-
   num_ids = ndev + 1;
   num_ids_word = num_ids / 32;
   if ((num_ids_word * 32) < num_ids)
@@ -79,11 +77,21 @@ plic_t::plic_t(std::vector<processor_t*>& procs, bool smode, uint32_t ndev)
   memset(priority, 0, sizeof(priority));
   memset(level, 0, sizeof(level));
 
-  for (size_t i = 0; i < contexts.size(); i++) {
-    plic_context_t* c = &contexts[i];
-    memset(c, 0, sizeof(*c));
-    c->proc = procs[i / contexts_per_hart];
-    c->mmode = (i % contexts_per_hart == 0);
+  // PLIC contexts are contiguous in memory even if harts are discontiguous.
+  for (const auto& [hart_id, hart] : sim->get_harts()) {
+    contexts.push_back(plic_context_t());
+    plic_context_t* m_context = &contexts.back();
+    memset(m_context, 0, sizeof(*m_context));
+    m_context->proc = hart;
+    m_context->mmode = true;
+
+    if (hart->extension_enabled_const('S')) {
+      contexts.push_back(plic_context_t());
+      plic_context_t* s_context = &contexts.back();
+      memset(s_context, 0, sizeof(*s_context));
+      s_context->proc = hart;
+      s_context->mmode = false;
+    }
   }
 }
 
diff --git a/riscv/sim.cc b/riscv/sim.cc
index 274a7c2..4e5e9a7 100644
--- a/riscv/sim.cc
+++ b/riscv/sim.cc
@@ -127,7 +127,7 @@ sim_t::sim_t(const cfg_t *cfg, bool halted,
   reg_t plic_base;
   uint32_t plic_ndev;
   if (fdt_parse_plic(fdt, &plic_base, &plic_ndev, "riscv,plic0") == 0) {
-    plic.reset(new plic_t(procs, true, plic_ndev));
+    plic.reset(new plic_t(this, plic_ndev));
     bus.add_device(plic_base, plic.get());
     intctrl = plic.get();
   }