[UNIKRAFT PATCH 2/2] plat/kvm/x86/tscclock: start from zero

[Hugo Lefeuvre <hugo.lefeuvre@xxxxxxxxx>]

The starting point of our monotonic clock is currently the initial value
of the TSC, converted to nanoseconds.

Start from zero instead: this allows for easier interpretation of
timestamps in debug messages.

Signed-off-by: Hugo Lefeuvre <hugo.lefeuvre@xxxxxxxxx>
---
 plat/kvm/x86/tscclock.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/plat/kvm/x86/tscclock.c b/plat/kvm/x86/tscclock.c
index e477088..bfe801c 100644
--- a/plat/kvm/x86/tscclock.c
+++ b/plat/kvm/x86/tscclock.c
@@ -256,24 +256,29 @@ int tscclock_init(void)
                tsc_freq = (rdtsc() - tsc_base) * 10;
        }
 
-       uk_pr_info("Clock source: TSC, frequency estimate is %llu Hz\n",
-                  (unsigned long long) tsc_freq);
-
        /*
         * Calculate TSC scaling multiplier.
         *
         * (0.32) tsc_mult = UKARCH_NSEC_PER_SEC (32.32) / tsc_freq (32.0)
         *
+        * Warning, do not print anything between TSC calibration and the
+        * setting of tsc_mult: if CONFIG_LIBUKDEBUG_PRINT_TIME is enabled
+        * this will trigger a reset of tsc_base via tscclock_monotonic
+        * and delay the clock starting point.
+        *
         * FIXME: this will overflow with small TSC frequencies. We should
         * probably calculate the TSC shift dynamically like solo5/hvt does.
         */
        tsc_mult = (UKARCH_NSEC_PER_SEC << 32) / tsc_freq;
 
+       uk_pr_info("Clock source: TSC, frequency estimate is %llu Hz\n",
+                  (unsigned long long) tsc_freq);
+
        /*
         * Monotonic time begins at tsc_base (first read of TSC before
         * calibration).
         */
-       time_base = mul64_32(tsc_base, tsc_mult);
+       tscclock_monotonic();
 
        /*
         * Compute RTC epoch offset by subtracting monotonic time_base from RTC
-- 
2.7.4