[PATCH v3 02/11] hvm/hpet: Only call guest_time_hpet(h) one time per action.

[Don Slutz <dslutz@verizon.com>]

This call is expensive and will cause extra time to pass.

The software-developers-hpet-spec-1-0a.pdf does not say how long it
takes after the main clock is enabled before the first change of the
master clock.  Therefore multiple calls to guest_time_hpet(h) are
not needed.  Since each timer is started by a loop, each ones start
time will change on the multple calls.  In the real hardware, there
is not delta based on which timer.

Without this change it is possible for an HVM guest running linux to
get the message:

..MP-BIOS bug: 8254 timer not connected to IO-APIC

On the guest console(s); and the guest will panic.

Also Xen hypervisor console with be flooded with:

vioapic.c:352:d1 Unsupported delivery mode 7
vioapic.c:352:d1 Unsupported delivery mode 7
vioapic.c:352:d1 Unsupported delivery mode 7

Signed-off-by: Don Slutz <dslutz@verizon.com>
---
v3:
  Did not add Reviewed-by (Jan Beulich) do to amount of change
  Added passing of guest_time to hpet_read64() and
    hpet_stop_timer().
  Dropped mc_starting.         

 xen/arch/x86/hvm/hpet.c | 55 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 34 insertions(+), 21 deletions(-)

diff --git a/xen/arch/x86/hvm/hpet.c b/xen/arch/x86/hvm/hpet.c
index 42c93f3..4fd6470 100644
--- a/xen/arch/x86/hvm/hpet.c
+++ b/xen/arch/x86/hvm/hpet.c
@@ -75,17 +75,18 @@
     ((timer_config(h, n) & HPET_TN_INT_ROUTE_CAP_MASK) \
         >> HPET_TN_INT_ROUTE_CAP_SHIFT)
 
-static inline uint64_t hpet_read_maincounter(HPETState *h)
+static inline uint64_t hpet_read_maincounter(HPETState *h, uint64_t guest_time)
 {
     ASSERT(spin_is_locked(&h->lock));
 
     if ( hpet_enabled(h) )
-        return guest_time_hpet(h) + h->mc_offset;
+        return guest_time + h->mc_offset;
     else
         return h->hpet.mc64;
 }
 
-static uint64_t hpet_get_comparator(HPETState *h, unsigned int tn)
+static uint64_t hpet_get_comparator(HPETState *h, unsigned int tn,
+                                    uint64_t guest_time)
 {
     uint64_t comparator;
     uint64_t elapsed;
@@ -97,7 +98,8 @@ static uint64_t hpet_get_comparator(HPETState *h, unsigned int tn)
         uint64_t period = h->hpet.period[tn];
         if (period)
         {
-            elapsed = hpet_read_maincounter(h) + period - 1 - comparator;
+            elapsed = hpet_read_maincounter(h, guest_time) +
+                period - 1 - comparator;
             comparator += (elapsed / period) * period;
             h->hpet.comparator64[tn] = comparator;
         }
@@ -109,7 +111,8 @@ static uint64_t hpet_get_comparator(HPETState *h, unsigned int tn)
     h->hpet.timers[tn].cmp = comparator;
     return comparator;
 }
-static inline uint64_t hpet_read64(HPETState *h, unsigned long addr)
+static inline uint64_t hpet_read64(HPETState *h, unsigned long addr,
+                                   uint64_t guest_time)
 {
     addr &= ~7;
 
@@ -122,7 +125,7 @@ static inline uint64_t hpet_read64(HPETState *h, unsigned long addr)
     case HPET_STATUS:
         return h->hpet.isr;
     case HPET_COUNTER:
-        return hpet_read_maincounter(h);
+        return hpet_read_maincounter(h, guest_time);
     case HPET_Tn_CFG(0):
     case HPET_Tn_CFG(1):
     case HPET_Tn_CFG(2):
@@ -130,7 +133,7 @@ static inline uint64_t hpet_read64(HPETState *h, unsigned long addr)
     case HPET_Tn_CMP(0):
     case HPET_Tn_CMP(1):
     case HPET_Tn_CMP(2):
-        return hpet_get_comparator(h, HPET_TN(CMP, addr));
+        return hpet_get_comparator(h, HPET_TN(CMP, addr), guest_time);
     case HPET_Tn_ROUTE(0):
     case HPET_Tn_ROUTE(1):
     case HPET_Tn_ROUTE(2):
@@ -176,7 +179,7 @@ static int hpet_read(
 
     spin_lock(&h->lock);
 
-    val = hpet_read64(h, addr);
+    val = hpet_read64(h, addr, guest_time_hpet(h));
 
     result = val;
     if ( length != 8 )
@@ -189,7 +192,8 @@ static int hpet_read(
     return X86EMUL_OKAY;
 }
 
-static void hpet_stop_timer(HPETState *h, unsigned int tn)
+static void hpet_stop_timer(HPETState *h, unsigned int tn,
+                            uint64_t guest_time)
 {
     ASSERT(tn < HPET_TIMER_NUM);
     ASSERT(spin_is_locked(&h->lock));
@@ -197,14 +201,15 @@ static void hpet_stop_timer(HPETState *h, unsigned int tn)
     destroy_periodic_time(&h->pt[tn]);
     /* read the comparator to get it updated so a read while stopped will
      * return the expected value. */
-    hpet_get_comparator(h, tn);
+    hpet_get_comparator(h, tn, guest_time);
 }
 
 /* the number of HPET tick that stands for
  * 1/(2^10) second, namely, 0.9765625 milliseconds */
 #define  HPET_TINY_TIME_SPAN  ((h->stime_freq >> 10) / STIME_PER_HPET_TICK)
 
-static void hpet_set_timer(HPETState *h, unsigned int tn)
+static void hpet_set_timer(HPETState *h, unsigned int tn,
+                           uint64_t guest_time)
 {
     uint64_t tn_cmp, cur_tick, diff;
     unsigned int irq;
@@ -223,8 +228,8 @@ static void hpet_set_timer(HPETState *h, unsigned int tn)
     if ( !timer_enabled(h, tn) )
         return;
 
-    tn_cmp   = hpet_get_comparator(h, tn);
-    cur_tick = hpet_read_maincounter(h);
+    tn_cmp   = hpet_get_comparator(h, tn, guest_time);
+    cur_tick = hpet_read_maincounter(h, guest_time);
     if ( timer_is_32bit(h, tn) )
     {
         tn_cmp   = (uint32_t)tn_cmp;
@@ -282,6 +287,7 @@ static int hpet_write(
 {
     HPETState *h = vcpu_vhpet(v);
     uint64_t old_val, new_val;
+    uint64_t guest_time;
     int tn, i;
 
     /* Acculumate a bit mask of timers whos state is changed by this write. */
@@ -298,7 +304,8 @@ static int hpet_write(
 
     spin_lock(&h->lock);
 
-    old_val = hpet_read64(h, addr);
+    guest_time = guest_time_hpet(h);
+    old_val = hpet_read64(h, addr, guest_time);
     new_val = val;
     if ( length != 8 )
         new_val = hpet_fixup_reg(
@@ -313,7 +320,7 @@ static int hpet_write(
         if ( !(old_val & HPET_CFG_ENABLE) && (new_val & HPET_CFG_ENABLE) )
         {
             /* Enable main counter and interrupt generation. */
-            h->mc_offset = h->hpet.mc64 - guest_time_hpet(h);
+            h->mc_offset = h->hpet.mc64 - guest_time;
             for ( i = 0; i < HPET_TIMER_NUM; i++ )
             {
                 h->hpet.comparator64[i] =
@@ -327,7 +334,7 @@ static int hpet_write(
         else if ( (old_val & HPET_CFG_ENABLE) && !(new_val & HPET_CFG_ENABLE) )
         {
             /* Halt main counter and disable interrupt generation. */
-            h->hpet.mc64 = h->mc_offset + guest_time_hpet(h);
+            h->hpet.mc64 = h->mc_offset + guest_time;
             for ( i = 0; i < HPET_TIMER_NUM; i++ )
                 if ( timer_enabled(h, i) )
                     set_stop_timer(i);
@@ -441,14 +448,14 @@ static int hpet_write(
     {
         i = find_first_set_bit(stop_timers);
         __clear_bit(i, &stop_timers);
-        hpet_stop_timer(h, i);
+        hpet_stop_timer(h, i, guest_time);
     }
 
     while (start_timers)
     {
         i = find_first_set_bit(start_timers);
         __clear_bit(i, &start_timers);
-        hpet_set_timer(h, i);
+        hpet_set_timer(h, i, guest_time);
     }
 
 #undef set_stop_timer
@@ -524,6 +531,7 @@ static int hpet_load(struct domain *d, hvm_domain_context_t *h)
     HPETState *hp = domain_vhpet(d);
     struct hvm_hw_hpet *rec;
     uint64_t cmp;
+    uint64_t guest_time;
     int i;
 
     spin_lock(&hp->lock);
@@ -562,14 +570,15 @@ static int hpet_load(struct domain *d, hvm_domain_context_t *h)
 #undef C
 
     /* Recalculate the offset between the main counter and guest time */
-    hp->mc_offset = hp->hpet.mc64 - guest_time_hpet(hp);
+    guest_time = guest_time_hpet(hp);
+    hp->mc_offset = hp->hpet.mc64 - guest_time;
 
     /* restart all timers */
 
     if ( hpet_enabled(hp) )
         for ( i = 0; i < HPET_TIMER_NUM; i++ )
             if ( timer_enabled(hp, i) )
-                hpet_set_timer(hp, i);
+                hpet_set_timer(hp, i, guest_time);
 
     spin_unlock(&hp->lock);
 
@@ -617,9 +626,13 @@ void hpet_deinit(struct domain *d)
     spin_lock(&h->lock);
 
     if ( hpet_enabled(h) )
+    {
+        uint64_t guest_time = guest_time_hpet(h);
+
         for ( i = 0; i < HPET_TIMER_NUM; i++ )
             if ( timer_enabled(h, i) )
-                hpet_stop_timer(h, i);
+                hpet_stop_timer(h, i, guest_time);
+    }
 
     spin_unlock(&h->lock);
 }
-- 
1.8.4