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Commit dc2babfe authored by Bharat Bhushan's avatar Bharat Bhushan Committed by Avi Kivity
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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: default avatarBharat Bhushan <bharat.bhushan@freescale.com>
Acked-by: default avatarLiu Yu <yu.liu@freescale.com>
Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent f9208427

arch/powerpc/kvm/emulate.c

+7 −5
Original line number Diff line number Diff line
@@ -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);