From: Patrick G. Bridges Date: Thu, 21 Oct 2010 17:22:21 +0000 (-0600) Subject: More minor fixes on time keeping. VMM clock now appears to be essentially accurate... X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=commitdiff_plain;h=99335f2927daf2c522ecb9ea246fbd68dd2000bb;p=palacios.git More minor fixes on time keeping. VMM clock now appears to be essentially accurate to real time on QEMU --- diff --git a/palacios/include/palacios/vmm_time.h b/palacios/include/palacios/vmm_time.h index 4364358..74c7584 100644 --- a/palacios/include/palacios/vmm_time.h +++ b/palacios/include/palacios/vmm_time.h @@ -48,9 +48,6 @@ struct vm_time { struct list_head timers; }; - - - struct vm_timer_ops { void (*update_timer)(struct guest_info * info, ullong_t cpu_cycles, ullong_t cpu_freq, void * priv_data); void (*advance_timer)(struct guest_info * info, void * private_data); @@ -63,19 +60,17 @@ struct vm_timer { struct list_head timer_link; }; +// Basic functions for handling passage of time in palacios +void v3_init_time(struct guest_info * info); +int v3_start_time(struct guest_info * info); +int v3_adjust_time(struct guest_info * info); - - +// Basic functions for attaching timers to the passage of time int v3_add_timer(struct guest_info * info, struct vm_timer_ops * ops, void * private_data); int v3_remove_timer(struct guest_info * info, struct vm_timer * timer); void v3_update_timers(struct guest_info * info); - -void v3_init_time(struct guest_info * info); -int v3_start_time(struct guest_info * info); -int v3_adjust_time(struct guest_info * info); - -// Returns host time +// Functions to return the different notions of time in Palacios. static inline uint64_t v3_get_host_time(struct vm_time *t) { uint64_t tmp; rdtscll(tmp); @@ -97,13 +92,17 @@ static inline sint64_t v3_tsc_host_offset(struct vm_time *time_state) { return time_state->guest_host_offset + time_state->tsc_guest_offset; } - +// Functions for handling exits on the TSC when fully virtualizing +// the timestamp counter. #define TSC_MSR 0x10 #define TSC_AUX_MSR 0xC0000103 int v3_handle_rdtscp(struct guest_info *info); int v3_handle_rdtsc(struct guest_info *info); + + + #endif // !__V3VEE__ #endif diff --git a/palacios/src/palacios/svm.c b/palacios/src/palacios/svm.c index 3ac98d4..35f2047 100644 --- a/palacios/src/palacios/svm.c +++ b/palacios/src/palacios/svm.c @@ -480,14 +480,16 @@ int v3_svm_enter(struct guest_info * info) { v3_update_timers(info); + /* If this guest is frequency-lagged behind host time, wait + * for the appropriate host time before resuming the guest. */ + v3_adjust_time(info); + guest_ctrl->TSC_OFFSET = v3_tsc_host_offset(&info->time_state); //V3_Print("Calling v3_svm_launch\n"); v3_svm_launch((vmcb_t *)V3_PAddr(info->vmm_data), &(info->vm_regs), (vmcb_t *)host_vmcbs[info->cpu_id]); - v3_adjust_time(info); - //V3_Print("SVM Returned: Exit Code: %x, guest_rip=%lx\n", (uint32_t)(guest_ctrl->exit_code), (unsigned long)guest_state->rip); v3_last_exit = (uint32_t)(guest_ctrl->exit_code); diff --git a/palacios/src/palacios/vmm_time.c b/palacios/src/palacios/vmm_time.c index b04a266..44affe4 100644 --- a/palacios/src/palacios/vmm_time.c +++ b/palacios/src/palacios/vmm_time.c @@ -41,18 +41,31 @@ * the passage of time: * (1) The host timestamp counter - read directly from HW and never written * (2) A monotonic guest timestamp counter used to measure the progression of - * time in the guest. This is computed as a multipler/offset from (1) above + * time in the guest. This is computed using an offsets from (1) above. * (3) The actual guest timestamp counter (which can be written by * writing to the guest TSC MSR - MSR 0x10) from the monotonic guest TSC. * This is also computed as an offset from (2) above when the TSC and * this offset is updated when the TSC MSR is written. * + * The value used to offset the guest TSC from the host TSC is the *sum* of all + * of these offsets (2 and 3) above + * * Because all other devices are slaved off of the passage of time in the guest, * it is (2) above that drives the firing of other timers in the guest, * including timer devices such as the Programmable Interrupt Timer (PIT). * - * - * + * Future additions: + * (1) Add support for temporarily skewing guest time off of where it should + * be to support slack simulation of guests. The idea is that simulators + * set this skew to be the difference between how much time passed for a + * simulated feature and a real implementation of that feature, making + * pass at a different rate from real time on this core. The VMM will then + * attempt to move this skew back towards 0 subject to resolution/accuracy + * constraints from various system timers. + * + * The main effort in doing this will be to get accuracy/resolution + * information from each local timer and to use this to bound how much skew + * is removed on each exit. */ @@ -89,20 +102,22 @@ int v3_adjust_time(struct guest_info * info) { } else { uint64_t guest_time, guest_elapsed, desired_elapsed; uint64_t host_time, target_host_time; + guest_time = v3_get_guest_time(time_state); + + /* Compute what host time this guest time should correspond to. */ 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; - host_time = v3_get_host_time(time_state); + /* Yield until that host time is reached */ + host_time = v3_get_host_time(time_state); while (host_time < target_host_time) { v3_yield(info); host_time = v3_get_host_time(time_state); } - time_state->guest_host_offset = guest_time - host_time; - + time_state->guest_host_offset = (sint64_t)guest_time - (sint64_t)host_time; } return 0; } @@ -306,3 +321,6 @@ void v3_init_time(struct guest_info * info) { + + + diff --git a/palacios/src/palacios/vmx.c b/palacios/src/palacios/vmx.c index beb2437..332e6ad 100644 --- a/palacios/src/palacios/vmx.c +++ b/palacios/src/palacios/vmx.c @@ -670,6 +670,10 @@ int v3_vmx_enter(struct guest_info * info) { v3_update_timers(info); + /* If this guest is frequency-lagged behind host time, wait + * for the appropriate host time before resuming the guest. */ + v3_adjust_time(info); + tsc_offset_high = (uint32_t)((v3_tsc_host_offset(&info->time_state) >> 32) & 0xffffffff); tsc_offset_low = (uint32_t)(v3_tsc_host_offset(&info->time_state) & 0xffffffff); check_vmcs_write(VMCS_TSC_OFFSET_HIGH, tsc_offset_high); @@ -695,10 +699,6 @@ int v3_vmx_enter(struct guest_info * info) { return -1; } - /* If this guest is frequency-lagged behind host time, wait - * for the appropriate host time. */ - v3_adjust_time(info); - info->num_exits++; /* Update guest state */