On Tue, 2009-09-29 at 10:18 +0200, Alexander Graf wrote:
> We support setting the DEC to a certain value right now. Doing that basically
> triggers the CPU local timer.
>
> But there's also an mfdec command that enabled the OS to read the decrementor.
>
> This is required at least by all desktop and server PowerPC Linux kernels. It
> can't really hurt to allow embedded ones to do it as well though.
>
> Signed-off-by: Alexander Graf <ag...@suse.de>
> ---
> arch/powerpc/kvm/emulate.c | 13 ++++++++++++-
> 1 files changed, 12 insertions(+), 1 deletions(-)
>
> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
> index 7737146..50d411d 100644
> --- a/arch/powerpc/kvm/emulate.c
> +++ b/arch/powerpc/kvm/emulate.c
> @@ -66,12 +66,14 @@
>
> void kvmppc_emulate_dec(struct kvm_vcpu *vcpu)
> {
> + unsigned long nr_jiffies;
> +
> if (vcpu->arch.tcr & TCR_DIE) {
> /* The decrementer ticks at the same rate as the timebase, so
> * that's how we convert the guest DEC value to the number of
> * host ticks. */
> - unsigned long nr_jiffies;
>
> + vcpu->arch.dec_jiffies = mftb();
> nr_jiffies = vcpu->arch.dec / tb_ticks_per_jiffy;
> mod_timer(&vcpu->arch.dec_timer,
> get_jiffies_64() + nr_jiffies);
> @@ -211,6 +213,15 @@ int kvmppc_emulate_instruction(struct kvm_run *run,
> struct kvm_vcpu *vcpu)
> /* Note: SPRG4-7 are user-readable, so we don't get
> * a trap. */
>
> + case SPRN_DEC:
> + {
> + u64 jd = mftb() - vcpu->arch.dec_jiffies;
> + vcpu->arch.gpr[rt] = vcpu->arch.dec - jd;
> +#ifdef DEBUG_EMUL
> + printk(KERN_INFO "mfDEC: %x - %llx = %lx\n",
> vcpu->arch.dec, jd, vcpu->arch.gpr[rt]);
> +#endif
> + break;
> + }
> default:
> emulated = kvmppc_core_emulate_mfspr(vcpu,
> sprn, rt);
> if (emulated == EMULATE_FAIL) {
mftb() doesn't exist for ppc32, so we'll need to use the get_tb()
wrapper instead.
--
Hollis Blanchard
IBM Linux Technology Center
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