xen/arm: remove physical timer offset

The physical timer traps apply an offset so that time starts at 0 for
the guest. However, this offset is not currently applied to the physical
counter. Per the ARMv8 Reference Manual (ARM DDI 0487E.a), section
D11.2.4 Timers, the "Offset" between the counter and timer should be
zero for a physical timer. This removes the offset to make the timer and
counter consistent.

This also cleans up the physical timer implementation to better match
the virtual timer - both cval's now hold the hardware value.

In the case the guest sets cval to a time before Xen started, the correct
behavior is to expire the timer immediately. To do this, we set the expires
argument of set_timer to zero.

Signed-off-by: Jeff Kubascik <jeff.kubascik@dornerworks.com>
Acked-by: Julien Grall <julien@xen.org>
(cherry picked from commit f14f55b7ee295277c8dd09e37e0fa0902ccf7eb4)

diff --git a/xen/arch/arm/vtimer.c b/xen/arch/arm/vtimer.c
index e6aebdac9ee6ae330ae2cee029c8c10d53875bee..bb8ad4ef27ea2385555d985294a6d15b8012eb3b 100644 (file)
--- a/xen/arch/arm/vtimer.c
+++ b/xen/arch/arm/vtimer.c
@@ -62,7 +62,6 @@ static void virt_timer_expired(void *data)
 
 int domain_vtimer_init(struct domain *d, struct xen_arch_domainconfig *config)
 {
-    d->arch.phys_timer_base.offset = NOW();
     d->arch.virt_timer_base.offset = READ_SYSREG64(CNTPCT_EL0);
     d->time_offset_seconds = ticks_to_ns(d->arch.virt_timer_base.offset - boot_count);
     do_div(d->time_offset_seconds, 1000000000);
@@ -108,7 +107,6 @@ int vcpu_vtimer_init(struct vcpu *v)
 
     init_timer(&t->timer, phys_timer_expired, t, v->processor);
     t->ctl = 0;
-    t->cval = NOW();
     t->irq = d0
         ? timer_get_irq(TIMER_PHYS_NONSECURE_PPI)
         : GUEST_TIMER_PHYS_NS_PPI;
@@ -167,6 +165,7 @@ void virt_timer_restore(struct vcpu *v)
 static bool vtimer_cntp_ctl(struct cpu_user_regs *regs, uint32_t *r, bool read)
 {
     struct vcpu *v = current;
+    s_time_t expires;
 
     if ( !ACCESS_ALLOWED(regs, EL0PTEN) )
         return false;
@@ -184,8 +183,13 @@ static bool vtimer_cntp_ctl(struct cpu_user_regs *regs, uint32_t *r, bool read)
 
         if ( v->arch.phys_timer.ctl & CNTx_CTL_ENABLE )
         {
-            set_timer(&v->arch.phys_timer.timer,
-                      v->arch.phys_timer.cval + v->domain->arch.phys_timer_base.offset);
+            /*
+             * If cval is before the point Xen started, expire timer
+             * immediately.
+             */
+            expires = v->arch.phys_timer.cval > boot_count
+                      ? ticks_to_ns(v->arch.phys_timer.cval - boot_count) : 0;
+            set_timer(&v->arch.phys_timer.timer, expires);
         }
         else
             stop_timer(&v->arch.phys_timer.timer);
@@ -197,26 +201,31 @@ static bool vtimer_cntp_tval(struct cpu_user_regs *regs, uint32_t *r,
                              bool read)
 {
     struct vcpu *v = current;
-    s_time_t now;
+    uint64_t cntpct;
+    s_time_t expires;
 
     if ( !ACCESS_ALLOWED(regs, EL0PTEN) )
         return false;
 
-    now = NOW() - v->domain->arch.phys_timer_base.offset;
+    cntpct = get_cycles();
 
     if ( read )
     {
-        *r = (uint32_t)(ns_to_ticks(v->arch.phys_timer.cval - now) & 0xffffffffull);
+        *r = (uint32_t)((v->arch.phys_timer.cval - cntpct) & 0xffffffffull);
     }
     else
     {
-        v->arch.phys_timer.cval = now + ticks_to_ns(*r);
+        v->arch.phys_timer.cval = cntpct + *r;
         if ( v->arch.phys_timer.ctl & CNTx_CTL_ENABLE )
         {
             v->arch.phys_timer.ctl &= ~CNTx_CTL_PENDING;
-            set_timer(&v->arch.phys_timer.timer,
-                      v->arch.phys_timer.cval +
-                      v->domain->arch.phys_timer_base.offset);
+            /*
+             * If cval is before the point Xen started, expire timer
+             * immediately.
+             */
+            expires = v->arch.phys_timer.cval > boot_count
+                      ? ticks_to_ns(v->arch.phys_timer.cval - boot_count) : 0;
+            set_timer(&v->arch.phys_timer.timer, expires);
         }
     }
     return true;
@@ -226,23 +235,28 @@ static bool vtimer_cntp_cval(struct cpu_user_regs *regs, uint64_t *r,
                              bool read)
 {
     struct vcpu *v = current;
+    s_time_t expires;
 
     if ( !ACCESS_ALLOWED(regs, EL0PTEN) )
         return false;
 
     if ( read )
     {
-        *r = ns_to_ticks(v->arch.phys_timer.cval);
+        *r = v->arch.phys_timer.cval;
     }
     else
     {
-        v->arch.phys_timer.cval = ticks_to_ns(*r);
+        v->arch.phys_timer.cval = *r;
         if ( v->arch.phys_timer.ctl & CNTx_CTL_ENABLE )
         {
             v->arch.phys_timer.ctl &= ~CNTx_CTL_PENDING;
-            set_timer(&v->arch.phys_timer.timer,
-                      v->arch.phys_timer.cval +
-                      v->domain->arch.phys_timer_base.offset);
+            /*
+             * If cval is before the point Xen started, expire timer
+             * immediately.
+             */
+            expires = v->arch.phys_timer.cval > boot_count
+                      ? ticks_to_ns(v->arch.phys_timer.cval - boot_count) : 0;
+            set_timer(&v->arch.phys_timer.timer, expires);
         }
     }
     return true;

diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index 86ebdd2bcf254b75687cb4cc14f5c94993d7f9eb..16a7150a95e9df7161fc46801e9b69b2c826f513 100644 (file)
--- a/xen/include/asm-arm/domain.h
+++ b/xen/include/asm-arm/domain.h
@@ -65,9 +65,6 @@ struct arch_domain
         RELMEM_done,
     } relmem;
 
-    struct {
-        uint64_t offset;
-    } phys_timer_base;
     struct {
         uint64_t offset;
     } virt_timer_base;