X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=blobdiff_plain;f=palacios%2Fsrc%2Fpalacios%2Fvmm_time.c;h=2295b3fc90d8ac340ba93eef6dfbbacb10681bf0;hb=9a32111c4074aafd55cd9590a24bd5c751a6fe61;hp=fc2e37e812a019428717ef1929b4be6e0480b93f;hpb=a8627ddaccf49073eb04286c5ea4767e2903c351;p=palacios.git diff --git a/palacios/src/palacios/vmm_time.c b/palacios/src/palacios/vmm_time.c index fc2e37e..2295b3f 100644 --- a/palacios/src/palacios/vmm_time.c +++ b/palacios/src/palacios/vmm_time.c @@ -99,71 +99,114 @@ int v3_start_time(struct guest_info * info) { int v3_offset_time( struct guest_info * info, sint64_t offset ) { struct vm_time * time_state = &(info->time_state); -// PrintDebug("Adding additional offset of %lld to guest time.\n", offset); + PrintDebug("Adding additional offset of %lld to guest time.\n", offset); time_state->guest_host_offset += offset; return 0; } -// Control guest time in relation to host time so that the two stay -// appropriately synchronized to the extent possible. -int v3_adjust_time(struct guest_info * info) { +#ifdef V3_CONFIG_TIME_DILATION +static uint64_t compute_target_host_time(struct guest_info * info, uint64_t guest_time) +{ struct vm_time * time_state = &(info->time_state); - uint64_t host_time, target_host_time; - uint64_t guest_time, target_guest_time, old_guest_time; - uint64_t guest_elapsed, host_elapsed, desired_elapsed; - - /* Compute the target host time given how much time has *already* - * passed in the guest */ - guest_time = v3_get_guest_time(time_state); + uint64_t guest_elapsed, desired_elapsed; + guest_elapsed = (guest_time - time_state->initial_time); desired_elapsed = (guest_elapsed * time_state->host_cpu_freq) / time_state->guest_cpu_freq; - target_host_time = time_state->initial_time + desired_elapsed; + return time_state->initial_time + desired_elapsed; +} + +static uint64_t compute_target_guest_time(struct guest_info *info) +{ + struct vm_time * time_state = &(info->time_state); + uint64_t host_elapsed, desired_elapsed; + + host_elapsed = v3_get_host_time(time_state) - time_state->initial_time; + desired_elapsed = (host_elapsed * time_state->guest_cpu_freq) / time_state->host_cpu_freq; + + return time_state->initial_time + desired_elapsed; + +} + +/* Yield time in the host to deal with a guest that wants to run slower than + * the native host cycle frequency */ +static int yield_host_time(struct guest_info * info) { + struct vm_time * time_state = &(info->time_state); + uint64_t host_time, target_host_time; + uint64_t guest_time, old_guest_time; /* Now, let the host run while the guest is stopped to make the two - * sync up. */ + * sync up. Note that this doesn't assume that guest time is stopped; + * the offsetting in the next step will change add an offset to guest + * time to account for the time paused even if the geust isn't + * usually paused in the VMM. */ host_time = v3_get_host_time(time_state); - old_guest_time = v3_get_guest_time(time_state); + old_guest_time = v3_compute_guest_time(time_state, host_time); + target_host_time = compute_target_host_time(info, old_guest_time); while (target_host_time > host_time) { v3_yield(info); host_time = v3_get_host_time(time_state); } - guest_time = v3_get_guest_time(time_state); + guest_time = v3_compute_guest_time(time_state, host_time); - // We do *not* assume the guest timer was paused in the VM. If it was - // this offseting is 0. If it wasn't we need this. - v3_offset_time(info, (sint64_t)old_guest_time - (sint64_t)guest_time); + /* We do *not* assume the guest timer was paused in the VM. If it was + * this offseting is 0. If it wasn't, we need this. */ + v3_offset_time(info, (sint64_t)(old_guest_time - guest_time)); + + return 0; +} +static int skew_guest_time(struct guest_info * info) { + struct vm_time * time_state = &(info->time_state); + uint64_t target_guest_time, guest_time; /* Now the host may have gotten ahead of the guest because * yielding is a coarse grained thing. Figure out what guest time * we want to be at, and use the use the offsetting mechanism in * the VMM to make the guest run forward. We limit *how* much we skew * it forward to prevent the guest time making large jumps, * however. */ - host_elapsed = host_time - time_state->initial_time; - desired_elapsed = (host_elapsed * time_state->guest_cpu_freq) / time_state->host_cpu_freq; - target_guest_time = time_state->initial_time + desired_elapsed; + target_guest_time = compute_target_guest_time(info); + guest_time = v3_get_guest_time(time_state); if (guest_time < target_guest_time) { - uint64_t max_skew, desired_skew, skew; + sint64_t max_skew, desired_skew, skew; if (time_state->enter_time) { - max_skew = (time_state->exit_time - time_state->enter_time) / 10; + /* Limit forward skew to 10% of the amount the guest has + * run since we last could skew time */ + max_skew = (sint64_t)(guest_time - time_state->enter_time) / 10.0; } else { max_skew = 0; } - desired_skew = target_guest_time - guest_time; + desired_skew = (sint64_t)(target_guest_time - guest_time); skew = desired_skew > max_skew ? max_skew : desired_skew; -/* PrintDebug("Guest %llu cycles behind where it should be.\n", + PrintDebug("Guest %lld cycles behind where it should be.\n", desired_skew); - PrintDebug("Limit on forward skew is %llu. Skewing forward %llu.\n", - max_skew, skew); */ + PrintDebug("Limit on forward skew is %lld. Skewing forward %lld.\n", + max_skew, skew); v3_offset_time(info, skew); } - + + return 0; +} +#endif /* V3_CONFIG_TIME_DILATION */ + +// Control guest time in relation to host time so that the two stay +// appropriately synchronized to the extent possible. +int v3_adjust_time(struct guest_info * info) { + +#ifdef V3_CONFIG_TIME_DILATION + /* First deal with yielding if we want to slow down the guest */ + yield_host_time(info); + + /* Now, if the guest is too slow, (either from excess yielding above, + * or because the VMM is doing something that takes a long time to emulate) + * allow guest time to jump forward a bit */ + skew_guest_time(info); +#endif return 0; } @@ -183,17 +226,24 @@ int v3_time_enter_vm( struct guest_info * info ) { struct vm_time * time_state = &(info->time_state); - uint64_t guest_time, host_time; + uint64_t host_time; - guest_time = v3_get_guest_time(time_state); host_time = v3_get_host_time(time_state); time_state->enter_time = host_time; - time_state->guest_host_offset = guest_time - host_time; - - // Because we just modified the offset - shouldn't matter as this should be - // the last time-related call prior to entering the VMM, but worth it - // just in case. - time_state->exit_time = host_time; +#ifdef V3_CONFIG_TIME_DILATION + { + uint64_t guest_time; + sint64_t offset; + guest_time = v3_compute_guest_time(time_state, host_time); + // XXX we probably want to use an inline function to do these + // time differences to deal with sign and overflow carefully + offset = (sint64_t)guest_time - (sint64_t)host_time; + PrintDebug("v3_time_enter_vm: guest time offset %lld from host time.\n", offset); + time_state->guest_host_offset = offset; + } +#else + time_state->guest_host_offset = 0; +#endif return 0; } @@ -227,12 +277,14 @@ int v3_remove_timer(struct guest_info * info, struct v3_timer * timer) { void v3_update_timers(struct guest_info * info) { struct vm_time *time_state = &info->time_state; struct v3_timer * tmp_timer; - uint64_t old_time = info->time_state.last_update; sint64_t cycles; + uint64_t old_time = info->time_state.last_update; time_state->last_update = v3_get_guest_time(time_state); - cycles = time_state->last_update - old_time; + cycles = (sint64_t)(time_state->last_update - old_time); + V3_ASSERT(cycles >= 0); + // V3_Print("Updating timers with %lld elapsed cycles.\n", cycles); list_for_each_entry(tmp_timer, &(time_state->timers), timer_link) { tmp_timer->ops->update_timer(info, cycles, time_state->guest_cpu_freq, tmp_timer->private_data); }