Commit 8fa76162 authored by Wei Huang's avatar Wei Huang Committed by Marc Zyngier

KVM: arm/arm64: arch_timer: Fix CNTP_TVAL calculation

Recently the generic timer test of kvm-unit-tests failed to complete
(stalled) when a physical timer is being used. This issue is caused
by incorrect update of CNTP_CVAL when CNTP_TVAL is being accessed,
introduced by 'Commit 84135d3d ("KVM: arm/arm64: consolidate arch
timer trap handlers")'. According to Arm ARM, the read/write behavior
of accesses to the TVAL registers is expected to be:

  * READ: TimerValue = (CompareValue – (Counter - Offset)
  * WRITE: CompareValue = ((Counter - Offset) + Sign(TimerValue)

This patch fixes the TVAL read/write code path according to the
specification.

Fixes: 84135d3d ("KVM: arm/arm64: consolidate arch timer trap handlers")
Signed-off-by: default avatarWei Huang <wei@redhat.com>
[maz: commit message tidy-up]
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
parent 8324c3d5
...@@ -812,7 +812,7 @@ static u64 kvm_arm_timer_read(struct kvm_vcpu *vcpu, ...@@ -812,7 +812,7 @@ static u64 kvm_arm_timer_read(struct kvm_vcpu *vcpu,
switch (treg) { switch (treg) {
case TIMER_REG_TVAL: case TIMER_REG_TVAL:
val = kvm_phys_timer_read() - timer->cntvoff - timer->cnt_cval; val = timer->cnt_cval - kvm_phys_timer_read() + timer->cntvoff;
break; break;
case TIMER_REG_CTL: case TIMER_REG_CTL:
...@@ -858,7 +858,7 @@ static void kvm_arm_timer_write(struct kvm_vcpu *vcpu, ...@@ -858,7 +858,7 @@ static void kvm_arm_timer_write(struct kvm_vcpu *vcpu,
{ {
switch (treg) { switch (treg) {
case TIMER_REG_TVAL: case TIMER_REG_TVAL:
timer->cnt_cval = val - kvm_phys_timer_read() - timer->cntvoff; timer->cnt_cval = kvm_phys_timer_read() - timer->cntvoff + val;
break; break;
case TIMER_REG_CTL: case TIMER_REG_CTL:
......
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