Cleanly separate HTIF code; don't poll keyboard on timer interrupt

7 files changed, 92 insertions, 87 deletions

diff --git a/machine/htif.c b/machine/htif.c
new file mode 100644
index 0000000..a513305
--- /dev/null
+++ b/machine/htif.c
@@ -0,0 +1,78 @@
+#include "htif.h"
+#include "atomic.h"
+#include "mtrap.h"
+
+volatile uint64_t tohost __attribute__((aligned(64))) __attribute__((section("htif")));
+volatile uint64_t fromhost __attribute__((aligned(64))) __attribute__((section("htif")));
+volatile int htif_console_buf;
+static spinlock_t htif_lock = SPINLOCK_INIT;
+
+static void request_htif_keyboard_interrupt()
+{
+  assert(tohost == 0);
+  tohost = TOHOST_CMD(1, 0, 0);
+}
+
+static void __check_fromhost()
+{
+  // we should only be interrupted by keypresses
+  uint64_t fh = fromhost;
+  if (!fh)
+    return;
+  if (!(FROMHOST_DEV(fh) == 1 && FROMHOST_CMD(fh) == 0))
+    die("unexpected htif interrupt");
+  htif_console_buf = 1 + (uint8_t)FROMHOST_DATA(fh);
+  fromhost = 0;
+}
+
+int htif_console_getchar()
+{
+  if (spinlock_trylock(&htif_lock) == 0) {
+    __check_fromhost();
+    spinlock_unlock(&htif_lock);
+  }
+
+  int ch = atomic_swap(&htif_console_buf, -1);
+  if (ch >= 0)
+    request_htif_keyboard_interrupt();
+  return ch - 1;
+}
+
+static void do_tohost_fromhost(uintptr_t dev, uintptr_t cmd, uintptr_t data)
+{
+  spinlock_lock(&htif_lock);
+    while (tohost)
+      __check_fromhost();
+    tohost = TOHOST_CMD(dev, cmd, data);
+
+    while (1) {
+      uint64_t fh = fromhost;
+      if (fh) {
+        if (FROMHOST_DEV(fh) == dev && FROMHOST_CMD(fh) == cmd) {
+          fromhost = 0;
+          break;
+        }
+        __check_fromhost();
+      }
+    }
+  spinlock_unlock(&htif_lock);
+}
+
+uintptr_t htif_syscall(uintptr_t arg)
+{
+  do_tohost_fromhost(0, 0, arg);
+  return 0;
+}
+
+void htif_console_putchar(uint8_t ch)
+{
+  do_tohost_fromhost(1, 1, ch);
+}
+
+void htif_poweroff()
+{
+  while (1) {
+    fromhost = 0;
+    tohost = 1;
+  }
+}
diff --git a/machine/htif.h b/machine/htif.h
index 7107ddb..f47e965 100644
--- a/machine/htif.h
+++ b/machine/htif.h
@@ -15,4 +15,9 @@
 #define FROMHOST_CMD(fromhost_value) ((uint64_t)(fromhost_value) << 8 >> 56)
 #define FROMHOST_DATA(fromhost_value) ((uint64_t)(fromhost_value) << 16 >> 16)
 
+void htif_console_putchar(uint8_t);
+int htif_console_getchar();
+void htif_poweroff() __attribute__((noreturn));
+uintptr_t htif_syscall(uintptr_t);
+
 #endif
diff --git a/machine/machine.mk.in b/machine/machine.mk.in
index 6568dc5..e224982 100644
--- a/machine/machine.mk.in
+++ b/machine/machine.mk.in
@@ -18,6 +18,7 @@ machine_hdrs = \
 machine_c_srcs = \
   mtrap.c \
   minit.c \
+  htif.c \
   emulation.c \
   muldiv_emulation.c \
   fp_emulation.c \
diff --git a/machine/mcall.h b/machine/mcall.h
index 2096d16..ed5a28c 100644
--- a/machine/mcall.h
+++ b/machine/mcall.h
@@ -4,7 +4,6 @@
 #define MCALL_HART_ID 0
 #define MCALL_CONSOLE_PUTCHAR 1
 #define MCALL_CONSOLE_GETCHAR 2
-#define MCALL_HTIF_SYSCALL 3
 #define MCALL_SEND_IPI 4
 #define MCALL_CLEAR_IPI 5
 #define MCALL_SHUTDOWN 6
diff --git a/machine/mtrap.c b/machine/mtrap.c
index 34772b7..0ed27e9 100644
--- a/machine/mtrap.c
+++ b/machine/mtrap.c
@@ -8,10 +8,6 @@
 #include <stdarg.h>
 #include <stdio.h>
 
-volatile uint64_t tohost __attribute__((aligned(64))) __attribute__((section("htif")));
-volatile uint64_t fromhost __attribute__((aligned(64))) __attribute__((section("htif")));
-static spinlock_t htif_lock = SPINLOCK_INIT;
-
 void __attribute__((noreturn)) bad_trap()
 {
   die("machine mode: unhandlable trap %d @ %p", read_csr(mcause), read_csr(mepc));
@@ -22,81 +18,24 @@ static uintptr_t mcall_hart_id()
   return read_const_csr(mhartid);
 }
 
-static void request_htif_keyboard_interrupt()
-{
-  assert(tohost == 0);
-  tohost = TOHOST_CMD(1, 0, 0);
-}
-
-static void __htif_interrupt()
-{
-  // we should only be interrupted by keypresses
-  uint64_t fh = fromhost;
-  if (!fh)
-    return;
-  if (!(FROMHOST_DEV(fh) == 1 && FROMHOST_CMD(fh) == 0))
-    die("unexpected htif interrupt");
-  HLS()->console_ibuf = 1 + (uint8_t)FROMHOST_DATA(fh);
-  fromhost = 0;
-  set_csr(mip, MIP_SSIP);
-}
-
-static void do_tohost_fromhost(uintptr_t dev, uintptr_t cmd, uintptr_t data)
-{
-  spinlock_lock(&htif_lock);
-    while (tohost)
-      __htif_interrupt();
-    tohost = TOHOST_CMD(dev, cmd, data);
-
-    while (1) {
-      uint64_t fh = fromhost;
-      if (fh) {
-        if (FROMHOST_DEV(fh) == dev && FROMHOST_CMD(fh) == cmd) {
-          fromhost = 0;
-          break;
-        }
-        __htif_interrupt();
-      }
-    }
-  spinlock_unlock(&htif_lock);
-}
-
-static void htif_interrupt()
-{
-  if (spinlock_trylock(&htif_lock) == 0) {
-    __htif_interrupt();
-    spinlock_unlock(&htif_lock);
-  }
-}
-
 uintptr_t timer_interrupt()
 {
   // just send the timer interrupt to the supervisor
   clear_csr(mie, MIP_MTIP);
   set_csr(mip, MIP_STIP);
 
-  // and poll the HTIF console
-  htif_interrupt();
-
   return 0;
 }
 
 static uintptr_t mcall_console_putchar(uint8_t ch)
 {
-  do_tohost_fromhost(1, 1, ch);
-  return 0;
-}
-
-static uintptr_t mcall_htif_syscall(uintptr_t magic_mem)
-{
-  do_tohost_fromhost(0, 0, magic_mem);
+  htif_console_putchar(ch);
   return 0;
 }
 
 void poweroff()
 {
-  while (1)
-    tohost = 1;
+  htif_poweroff();
 }
 
 void putstring(const char* s)
@@ -134,29 +73,16 @@ static uintptr_t mcall_send_ipi(uintptr_t recipient)
   return 0;
 }
 
-static void reset_ssip()
-{
-  clear_csr(mip, MIP_SSIP);
-  mb();
-
-  if (HLS()->sipi_pending || HLS()->console_ibuf > 0)
-    set_csr(mip, MIP_SSIP);
-}
-
 static uintptr_t mcall_console_getchar()
 {
-  int ch = atomic_swap(&HLS()->console_ibuf, -1);
-  if (ch >= 0)
-    request_htif_keyboard_interrupt();
-  reset_ssip();
-  return ch - 1;
+  return htif_console_getchar();
 }
 
 static uintptr_t mcall_clear_ipi()
 {
-  int ipi = atomic_swap(&HLS()->sipi_pending, 0);
-  reset_ssip();
-  return ipi;
+  clear_csr(mip, MIP_SSIP);
+  mb();
+  return atomic_swap(&HLS()->sipi_pending, 0);
 }
 
 static uintptr_t mcall_shutdown()
@@ -239,9 +165,6 @@ void mcall_trap(uintptr_t* regs, uintptr_t mcause, uintptr_t mepc)
     case MCALL_CONSOLE_GETCHAR:
       retval = mcall_console_getchar();
       break;
-    case MCALL_HTIF_SYSCALL:
-      retval = mcall_htif_syscall(arg0);
-      break;
     case MCALL_SEND_IPI:
       retval = mcall_send_ipi(arg0);
       break;
diff --git a/machine/mtrap.h b/machine/mtrap.h
index 9995203..68c93f2 100644
--- a/machine/mtrap.h
+++ b/machine/mtrap.h
@@ -41,7 +41,6 @@ typedef struct {
   uint32_t* ipi;
   volatile int mipi_pending;
   volatile int sipi_pending;
-  int console_ibuf;
 
   volatile uint32_t* plic_m_thresh;
   volatile uintptr_t* plic_m_ie;
diff --git a/pk/frontend.c b/pk/frontend.c
index 13fdfcf..716f050 100644
--- a/pk/frontend.c
+++ b/pk/frontend.c
@@ -4,8 +4,8 @@
 #include "atomic.h"
 #include "frontend.h"
 #include "sbi.h"
-#include "mcall.h"
 #include "syscall.h"
+#include "htif.h"
 #include <stdint.h>
 
 long frontend_syscall(long n, uint64_t a0, uint64_t a1, uint64_t a2, uint64_t a3, uint64_t a4, uint64_t a5, uint64_t a6)
@@ -24,7 +24,7 @@ long frontend_syscall(long n, uint64_t a0, uint64_t a1, uint64_t a2, uint64_t a3
   magic_mem[6] = a5;
   magic_mem[7] = a6;
 
-  do_mcall(MCALL_HTIF_SYSCALL, magic_mem);
+  htif_syscall((uintptr_t)magic_mem);
 
   long ret = magic_mem[0];