In qemu/kvm, qemu emulates the pmtimer. Reading pmtimer in vm will cause a vm exit, and qemu read the real time. If the qemu thread is scheduled out before reading time, the time that vm reads may delay. In some case, pmtimer delta may be far more than 1ms, which cause tsc rate is much larger than real rate. So in grub menu, grub timeout will take more time than expected. So calculate tsc rate by the actual pmtimer delta, not always use 1ms.

This fixs cannot fix the issue completely, it just reduce the probability of the issue.

diff --git a/grub-core/kern/i386/tsc_pmtimer.c b/grub-core/kern/i386/tsc_pmtimer.c
index 5c03c510a..6d0802dfe 100644
--- a/grub-core/kern/i386/tsc_pmtimer.c
+++ b/grub-core/kern/i386/tsc_pmtimer.c
@@ -84,7 +84,7 @@ grub_pmtimer_wait_count_tsc (grub_port_t pmtimer,
                        cur - start);
          grub_dprintf ("pmtimer", "tsc delta is 0x%"PRIxGRUB_UINT64_T"\n",
                        end_tsc - start_tsc);
-         return end_tsc - start_tsc;
+         return (end_tsc - start_tsc) / (cur - start) * num_pm_ticks;
        }