The documentation for the Linux pvclock is pretty sparse but I am
pretty sure we want to use a monotonic base for ti_system_time. We
also have a function for converting a timespec into a 64-bit count of
nanoseconds we can use.
We may as well also use rdtsc_lfence() to ensure consistent behavior.
... this is still not quite right because the VM expects the pvclock
to have a fixed frequency, but we have no interface to reading a raw
timestamp. Something to add in the future, maybe.
Index: vmm.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/vmm.c,v
retrieving revision 1.284
diff -u -p -r1.284 vmm.c
--- vmm.c 18 May 2021 00:05:20 -0000 1.284
+++ vmm.c 2 Jun 2021 00:57:31 -0000
@@ -7294,8 +7294,8 @@ vmm_init_pvclock(struct vcpu *vcpu, padd
int
vmm_update_pvclock(struct vcpu *vcpu)
{
+ struct timespec now;
struct pvclock_time_info *pvclock_ti;
- struct timespec tv;
struct vm *vm = vcpu->vc_parent;
paddr_t pvclock_hpa, pvclock_gpa;
@@ -7309,10 +7309,9 @@ vmm_update_pvclock(struct vcpu *vcpu)
pvclock_ti->ti_version =
(++vcpu->vc_pvclock_version << 1) | 0x1;
- pvclock_ti->ti_tsc_timestamp = rdtsc();
- nanotime(&tv);
- pvclock_ti->ti_system_time =
- tv.tv_sec * 1000000000L + tv.tv_nsec;
+ pvclock_ti->ti_tsc_timestamp = rdtsc_lfence();
+ nanouptime(&now);
+ pvclock_ti->ti_system_time = TIMESPEC_TO_NSEC(&now);
pvclock_ti->ti_tsc_shift = 12;
pvclock_ti->ti_tsc_to_system_mul =
vcpu->vc_pvclock_system_tsc_mul;
