Redirecting the wakeup of a VCPU from the H_IPI hypercall to
a core running in the host is usually a good idea, most workloads
seemed to benefit. However, in one heavily interrupt-driven SMT1
workload, some regression was observed. This patch adds a kvm_hv
module parameter called h_ipi_redirect to control this feature.
The default value for this tunable is 1 - that is enable the feature.
Signed-off-by: Suresh Warrier <warr...@linux.vnet.ibm.com>
---
Resending the updated patch with the updated diff since an
earlier patch (patch 8/9) had to be resent to fix a build
break.
arch/powerpc/include/asm/kvm_ppc.h | 1 +
arch/powerpc/kvm/book3s_hv.c | 11 +++++++++++
arch/powerpc/kvm/book3s_hv_rm_xics.c | 5 ++++-
3 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/kvm_ppc.h
b/arch/powerpc/include/asm/kvm_ppc.h
index 1b93519..29d1442 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -448,6 +448,7 @@ extern int kvmppc_xics_set_icp(struct kvm_vcpu *vcpu, u64
icpval);
extern int kvmppc_xics_connect_vcpu(struct kvm_device *dev,
struct kvm_vcpu *vcpu, u32 cpu);
extern void kvmppc_xics_ipi_action(void);
+extern int h_ipi_redirect;
#else
static inline void kvmppc_alloc_host_rm_ops(void) {};
static inline void kvmppc_free_host_rm_ops(void) {};
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index d6280ed..182ec84 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -81,6 +81,17 @@ static int target_smt_mode;
module_param(target_smt_mode, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(target_smt_mode, "Target threads per core (0 = max)");
+#ifdef CONFIG_KVM_XICS
+static struct kernel_param_ops module_param_ops = {
+ .set = param_set_int,
+ .get = param_get_int,
+};
+
+module_param_cb(h_ipi_redirect, &module_param_ops, &h_ipi_redirect,
+ S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(h_ipi_redirect, "Redirect H_IPI wakeup to a free host core");
+#endif
+
static void kvmppc_end_cede(struct kvm_vcpu *vcpu);
static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu);
diff --git a/arch/powerpc/kvm/book3s_hv_rm_xics.c
b/arch/powerpc/kvm/book3s_hv_rm_xics.c
index e673fb9..980d8a6 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_xics.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_xics.c
@@ -24,6 +24,9 @@
#define DEBUG_PASSUP
+int h_ipi_redirect = 1;
+EXPORT_SYMBOL(h_ipi_redirect);
+
static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp
*icp,
u32 new_irq);
@@ -148,7 +151,7 @@ static void icp_rm_set_vcpu_irq(struct kvm_vcpu *vcpu,
cpu = vcpu->arch.thread_cpu;
if (cpu < 0 || cpu >= nr_cpu_ids) {
hcore = -1;
- if (kvmppc_host_rm_ops_hv)
+ if (kvmppc_host_rm_ops_hv && h_ipi_redirect)
hcore = find_available_hostcore(XICS_RM_KICK_VCPU);
if (hcore != -1) {
icp_send_hcore_msg(hcore, vcpu);
--
1.8.3.4
--
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