From 55f7d4b09e0bd1f6e5875fe0a5a58852999e4e92 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Sun, 16 Oct 2011 19:26:17 +0000 Subject: [PATCH] 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 Signed-off-by: David Gibson Signed-off-by: Alexander Graf --- hw/ppc.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/hw/ppc.c b/hw/ppc.c index 25b59dddaa..d29af0bb35 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) { -- 2.11.4.GIT