| Message ID | 20190329201253.29164-1-wei@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [1/1] KVM: arm/arm64: arch_timer: Fix TimerValue TVAL calculation in KVM | expand |
On Fri, 29 Mar 2019 20:12:53 +0000, Wei Huang <wei@redhat.com> wrote: > > 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 CNT_CVAL when TimerValue is being accessed, > introduced by 'Commit 84135d3d18da ("KVM: arm/arm64: consolidate arch > timer trap handlers")'. According to Arm ARM, the read/write behavior > of accesses to TimeValue 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. > > Signed-off-by: Wei Huang <wei@redhat.com> Huh... Nice catch. I guess I only ran this with a VHE host, where this code path is unused. Thanks, M.
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index 3417f2dbc366..d43308dc3617 100644 --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -812,7 +812,7 @@ static u64 kvm_arm_timer_read(struct kvm_vcpu *vcpu, switch (treg) { 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; case TIMER_REG_CTL: @@ -858,7 +858,7 @@ static void kvm_arm_timer_write(struct kvm_vcpu *vcpu, { switch (treg) { 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; case TIMER_REG_CTL:
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 CNT_CVAL when TimerValue is being accessed, introduced by 'Commit 84135d3d18da ("KVM: arm/arm64: consolidate arch timer trap handlers")'. According to Arm ARM, the read/write behavior of accesses to TimeValue 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. Signed-off-by: Wei Huang <wei@redhat.com> --- virt/kvm/arm/arch_timer.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)