[PATCH 09/52] Fix DEC truncation for greater than 0xffff_ffff/1000

Alexander Graf
2012-01-13T14:58:36Z

From: Bharat Bhushan <r65777@freescale.com>

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>
---
arch/powerpc/kvm/emulate.c | 12 +++++++-----
1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
index 141dce3..4337f99 100644
--- 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);
--
1.6.0.2