[Xen-devel] [PATCH] xen/arm: remove physical timer offset

[Jeff Kubascik <jeff.kubascik@dornerworks.com>]

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 Arch Reference Manual, the offset between the
physical timer and counter should be 0. This removes the offset to make
the timer and counter consistent.

Xen time is at offset boot_count from the physical counter, so we need
to take this into account when reading/writing to CNTP_CVAL.

Signed-off-by: Jeff Kubascik <jeff.kubascik@dornerworks.com>
---
 xen/arch/arm/vtimer.c        | 18 ++++++------------
 xen/include/asm-arm/domain.h |  3 ---
 2 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/xen/arch/arm/vtimer.c b/xen/arch/arm/vtimer.c
index e6aebdac9e..4790b5ce58 100644
--- 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);
@@ -184,8 +183,7 @@ 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);
+            set_timer(&v->arch.phys_timer.timer, v->arch.phys_timer.cval);
         }
         else
             stop_timer(&v->arch.phys_timer.timer);
@@ -202,7 +200,7 @@ static bool vtimer_cntp_tval(struct cpu_user_regs *regs, uint32_t *r,
     if ( !ACCESS_ALLOWED(regs, EL0PTEN) )
         return false;
 
-    now = NOW() - v->domain->arch.phys_timer_base.offset;
+    now = NOW();
 
     if ( read )
     {
@@ -214,9 +212,7 @@ static bool vtimer_cntp_tval(struct cpu_user_regs *regs, uint32_t *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);
+            set_timer(&v->arch.phys_timer.timer, v->arch.phys_timer.cval);
         }
     }
     return true;
@@ -232,17 +228,15 @@ static bool vtimer_cntp_cval(struct cpu_user_regs *regs, uint64_t *r,
 
     if ( read )
     {
-        *r = ns_to_ticks(v->arch.phys_timer.cval);
+        *r = ns_to_ticks(v->arch.phys_timer.cval) + boot_count;
     }
     else
     {
-        v->arch.phys_timer.cval = ticks_to_ns(*r);
+        v->arch.phys_timer.cval = ticks_to_ns(*r - boot_count);
         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);
+            set_timer(&v->arch.phys_timer.timer, v->arch.phys_timer.cval);
         }
     }
     return true;
diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index 86ebdd2bcf..16a7150a95 100644
--- 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;
-- 
2.17.1


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