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authorDavid Gibson <david@gibson.dropbear.id.au>2011-10-16 19:26:17 +0000
committerAlexander Graf <agraf@suse.de>2011-10-30 20:03:26 +0100
commit55f7d4b09e0bd1f6e5875fe0a5a58852999e4e92 (patch)
tree9909c3e93d166e8583424b3ce82ac489f77f0ab3 /hw/ppc.c
parentf0ad8c340145b246982885addef1aac183790706 (diff)
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ppc: Avoid decrementer related kvm exits
In __cpu_ppc_store_decr(), we set up a regular timer used to trigger decrementer interrupts. This is necessary to implement the decrementer properly under TCG, but is unnecessary under KVM (true for both Book3S-PR and Book3S-HV KVM variants), because the kernel handles generating and delivering decrementer exceptions. Under kvm, in fact, the timer causes expensive and unnecessary exits from kvm to qemu. This patch, therefore, disables setting the timer when kvm is in use. Signed-off-by: Anton Blanchard <anton@au1.ibm.com> Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Alexander Graf <agraf@suse.de>
Diffstat (limited to 'hw/ppc.c')
-rw-r--r--hw/ppc.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/hw/ppc.c b/hw/ppc.c
index 25b59dd..d29af0b 100644
--- a/hw/ppc.c
+++ b/hw/ppc.c
@@ -662,6 +662,12 @@ static void __cpu_ppc_store_decr (CPUState *env, uint64_t *nextp,
LOG_TB("%s: %08" PRIx32 " => %08" PRIx32 "\n", __func__,
decr, value);
+
+ if (kvm_enabled()) {
+ /* KVM handles decrementer exceptions, we don't need our own timer */
+ return;
+ }
+
now = qemu_get_clock_ns(vm_clock);
next = now + muldiv64(value, get_ticks_per_sec(), tb_env->decr_freq);
if (is_excp) {