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Add mfdec emulation

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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 <agraf@suse.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Alexander Graf 2009-10-30 05:47:15 +00:00 committed by Benjamin Herrenschmidt
parent c215c6e49f
commit 9a7a9b09fe
1 changed files with 12 additions and 1 deletions
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13
arch/powerpc/kvm/emulate.c
View file

@ -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) {