[UNIKRAFT PATCH 1/2] plat/kvm/x86/tscclock: fix potentially uninitialized tsc_base

[Hugo Lefeuvre <hugo.lefeuvre@xxxxxxxxx>]

tsc_base might remain uninitialized if the TSC clock frequency is retrieved
from the hypervisor. This can potentially result in a small delay in the
clock starting point.

Make sure to initialize tsc_base when retrieving TSC clock frequency from
the hypervisor.

Signed-off-by: Hugo Lefeuvre <hugo.lefeuvre@xxxxxxxxx>
---
 plat/kvm/x86/tscclock.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/plat/kvm/x86/tscclock.c b/plat/kvm/x86/tscclock.c
index 727164a..e477088 100644
--- a/plat/kvm/x86/tscclock.c
+++ b/plat/kvm/x86/tscclock.c
@@ -194,7 +194,7 @@ static __u64 rtc_gettimeofday(void)
 }
 
 /*
- * Beturn monotonic time using TSC clock.
+ * Return monotonic time using TSC clock.
  */
 __u64 tscclock_monotonic(void)
 {
@@ -239,6 +239,7 @@ int tscclock_init(void)
        cpuid(0x40000000, 0, &eax, &ebx, &ecx, &edx);
        if (eax >= 0x40000010) {
                uk_pr_info("Retrieving TSC clock frequency from hypervisor\n");
+               tsc_base = rdtsc();
                cpuid(0x40000010, 0, &eax, &ebx, &ecx, &edx);
                tsc_freq = eax * 1000;
        }
@@ -262,6 +263,9 @@ int tscclock_init(void)
         * Calculate TSC scaling multiplier.
         *
         * (0.32) tsc_mult = UKARCH_NSEC_PER_SEC (32.32) / tsc_freq (32.0)
+        *
+        * 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;
 
-- 
2.7.4