Is UEFI required for ZFS?

[Konstantin Belousov]

On Sat, Feb 13, 2016 at 03:46:16PM +0000, Mark Dixon wrote:
> I don't think I can clock it down, although the UEFI bios screens are
> massively confusing so I could be wrong.
> 
> Verbose dmesg:

Might be, try the following (mostly debugging) change.

diff --git a/sys/boot/i386/libi386/time.c b/sys/boot/i386/libi386/time.c
index c27dcf6..592d64a 100644
--- a/sys/boot/i386/libi386/time.c
+++ b/sys/boot/i386/libi386/time.c
@@ -97,8 +97,8 @@ time(time_t *t)
  * Resolution of this function is variable, but typically around
  * 1ms.
  */
-void
-delay(int period)
+static void
+delay_bios(int period)
 {
     v86.ctl = 0;
     v86.addr = 0x15;		/* int 0x15, function 0x86 */
@@ -107,3 +107,53 @@ delay(int period)
     v86.edx = period & 0xffff;
     v86int();
 }
+
+static uint64_t rd;
+
+static __inline uint64_t
+rdtsc(void)
+{
+	uint64_t rv;
+
+	__asm __volatile("rdtsc" : "=A" (rv));
+	return (rv);
+}
+
+static void
+delay_rdtsc_calibrate(void)
+{
+	int x1, x2;
+	uint64_t s, f;
+
+	for (x1 = bios_seconds(); x1 == (x2 = bios_seconds());)
+		;
+	s = rdtsc();
+	for (; x2 == (x1 = bios_seconds());)
+		;
+	f = rdtsc();
+	rd = f - s;
+	printf("rd %llx\n", rd);
+}
+
+static void
+delay_rdtsc(int period)
+{
+	uint64_t x;
+
+	x = rdtsc() + rd / 1000000;
+	while (rdtsc() < x)
+		;
+}
+
+void
+delay(int period)
+{
+
+	if (0) {
+		delay_bios(period);
+	} else {
+		if (rd == 0)
+			delay_rdtsc_calibrate();
+		delay_rdtsc(period);
+	}
+}