KVM: PPC: Fix DEC truncation for greater than 0xffff_ffff/1000

kvmppc_emulate_dec() uses dec_nsec of type unsigned long and does below calculation:

        dec_nsec = vcpu->arch.dec;
        dec_nsec *= 1000;
This will truncate if DEC value "vcpu->arch.dec" is greater than 0xffff_ffff/1000.
For example : For tb_ticks_per_usec = 4a, we can not set decrementer more than ~58ms.

Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
Acked-by: Liu Yu <yu.liu@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
index 141dce3c6810839b65f519767c070d28c3c11fa0..4337f99fa0fa0706b57e8a343af8d04e9e3158b9 100644 (file)
--- a/arch/powerpc/kvm/emulate.c
+++ b/arch/powerpc/kvm/emulate.c
@@ -84,6 +84,7 @@ static int kvmppc_dec_enabled(struct kvm_vcpu *vcpu)
 void kvmppc_emulate_dec(struct kvm_vcpu *vcpu)
 {
        unsigned long dec_nsec;
+       unsigned long long dec_time;
 
        pr_debug("mtDEC: %x\n", vcpu->arch.dec);
 #ifdef CONFIG_PPC_BOOK3S
@@ -103,11 +104,12 @@ void kvmppc_emulate_dec(struct kvm_vcpu *vcpu)
                 * host ticks. */
 
                hrtimer_try_to_cancel(&vcpu->arch.dec_timer);
-               dec_nsec = vcpu->arch.dec;
-               dec_nsec *= 1000;
-               dec_nsec /= tb_ticks_per_usec;
-               hrtimer_start(&vcpu->arch.dec_timer, ktime_set(0, dec_nsec),
-                             HRTIMER_MODE_REL);
+               dec_time = vcpu->arch.dec;
+               dec_time *= 1000;
+               do_div(dec_time, tb_ticks_per_usec);
+               dec_nsec = do_div(dec_time, NSEC_PER_SEC);
+               hrtimer_start(&vcpu->arch.dec_timer,
+                       ktime_set(dec_time, dec_nsec), HRTIMER_MODE_REL);
                vcpu->arch.dec_jiffies = get_tb();
        } else {
                hrtimer_try_to_cancel(&vcpu->arch.dec_timer);