hvm: Build guest timers on monotonic system time.

Move hvm platform timers from underlying physical CPU TSC to Xen
system time and ensure domain-wide monotonicity. TSC on many systems
may skew between processors leading to 'time going backwards' messages
from some guests.

Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

4 files changed, 13 insertions, 4 deletions

diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 815a5c2b02..e871bf8be7 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -147,8 +147,10 @@ void hvm_send_assist_req(struct vcpu *v);
 
 void hvm_set_guest_tsc(struct vcpu *v, u64 guest_tsc);
 u64 hvm_get_guest_tsc(struct vcpu *v);
-#define hvm_set_guest_time(vcpu, gtime) hvm_set_guest_tsc(vcpu, gtime)
-#define hvm_get_guest_time(vcpu)        hvm_get_guest_tsc(vcpu)
+
+void hvm_init_guest_time(struct domain *d);
+void hvm_set_guest_time(struct vcpu *v, u64 guest_time);
+u64 hvm_get_guest_time(struct vcpu *v);
 
 #define hvm_paging_enabled(v) \
     (!!((v)->arch.hvm_vcpu.guest_cr[0] & X86_CR0_PG))
diff --git a/xen/include/asm-x86/hvm/vcpu.h b/xen/include/asm-x86/hvm/vcpu.h
index fc43d5d20d..6eb9d67b73 100644
--- a/xen/include/asm-x86/hvm/vcpu.h
+++ b/xen/include/asm-x86/hvm/vcpu.h
@@ -68,6 +68,9 @@ struct hvm_vcpu {
     struct mtrr_state   mtrr;
     u64                 pat_cr;
 
+    /* In mode delay_for_missed_ticks, VCPUs have differing guest times. */
+    int64_t             stime_offset;
+
     /* Which cache mode is this VCPU in (CR0:CD/NW)? */
     u8                  cache_mode;
 
diff --git a/xen/include/asm-x86/hvm/vmx/vmx.h b/xen/include/asm-x86/hvm/vmx/vmx.h
index b7681f0e29..0e381f7e1d 100644
--- a/xen/include/asm-x86/hvm/vmx/vmx.h
+++ b/xen/include/asm-x86/hvm/vmx/vmx.h
@@ -49,7 +49,6 @@ void vmx_asm_vmexit_handler(struct cpu_user_regs);
 void vmx_asm_do_vmentry(void);
 void vmx_intr_assist(void);
 void vmx_do_resume(struct vcpu *);
-void set_guest_time(struct vcpu *v, u64 gtime);
 void vmx_vlapic_msr_changed(struct vcpu *v);
 void vmx_realmode(struct cpu_user_regs *regs);
 
diff --git a/xen/include/asm-x86/hvm/vpt.h b/xen/include/asm-x86/hvm/vpt.h
index ddc099975d..24026fb118 100644
--- a/xen/include/asm-x86/hvm/vpt.h
+++ b/xen/include/asm-x86/hvm/vpt.h
@@ -57,7 +57,7 @@ struct hpet_registers {
 typedef struct HPETState {
     struct hpet_registers hpet;
     struct vcpu *vcpu;
-    uint64_t tsc_freq;
+    uint64_t stime_freq;
     uint64_t hpet_to_ns_scale; /* hpet ticks to ns (multiplied by 2^10) */
     uint64_t hpet_to_ns_limit; /* max hpet ticks convertable to ns      */
     uint64_t mc_offset;
@@ -137,6 +137,11 @@ struct pl_time {    /* platform time */
     struct RTCState  vrtc;
     struct HPETState vhpet;
     struct PMTState  vpmt;
+    /* guest_time = Xen sys time + stime_offset */
+    int64_t stime_offset;
+    /* Ensures monotonicity in appropriate timer modes. */
+    uint64_t last_guest_time;
+    spinlock_t pl_time_lock;
 };
 
 #define ticks_per_sec(v) (v->domain->arch.hvm_domain.tsc_frequency)