commit 7d050527e3f5cadbf9db3bce09409fb4e9259997
author Suraj Jitindar Singh <sjitindarsingh@gmail.com> Fri Mar 01 13:43:16 2019 +1100
committer David Gibson <david@gibson.dropbear.id.au> Tue Mar 12 12:07:49 2019 +1100
tree 04a611677693b7cc316124bf48f246add523d257
parent a8dafa525181e57405b7ef4bf7c212bf5f6d8ca1

target/ppc: Implement large decrementer support for KVM

Implement support to allow KVM guests to take advantage of the large
decrementer introduced on POWER9 cpus.

To determine if the host can support the requested large decrementer
size, we check it matches that specified in the ibm,dec-bits device-tree
property. We also need to enable it in KVM by setting the LPCR_LD bit in
the LPCR. Note that to do this we need to try and set the bit, then read
it back to check the host allowed us to set it, if so we can use it but
if we were unable to set it the host cannot support it and we must not
use the large decrementer.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20190301024317.22137-3-sjitindarsingh@gmail.com>
[dwg: Small style fixes]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

target/ppc/kvm.c

diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
index d01852f..f0f5bf9 100644
--- a/target/ppc/kvm.c
+++ b/target/ppc/kvm.c
@@ -91,6 +91,7 @@
 static int cap_ppc_safe_bounds_check;
 static int cap_ppc_safe_indirect_branch;
 static int cap_ppc_nested_kvm_hv;
+static int cap_large_decr;
 
 static uint32_t debug_inst_opcode;
 
@@ -124,6 +125,7 @@
 
 static int kvm_ppc_register_host_cpu_type(MachineState *ms);
 static void kvmppc_get_cpu_characteristics(KVMState *s);
+static int kvmppc_get_dec_bits(void);
 
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
@@ -151,6 +153,7 @@
     cap_resize_hpt = kvm_vm_check_extension(s, KVM_CAP_SPAPR_RESIZE_HPT);
     kvmppc_get_cpu_characteristics(s);
     cap_ppc_nested_kvm_hv = kvm_vm_check_extension(s, KVM_CAP_PPC_NESTED_HV);
+    cap_large_decr = kvmppc_get_dec_bits();
     /*
      * Note: setting it to false because there is not such capability
      * in KVM at this moment.
@@ -1927,6 +1930,16 @@
     return kvmppc_read_int_cpu_dt("clock-frequency");
 }
 
+static int kvmppc_get_dec_bits(void)
+{
+    int nr_bits = kvmppc_read_int_cpu_dt("ibm,dec-bits");
+
+    if (nr_bits > 0) {
+        return nr_bits;
+    }
+    return 0;
+}
+
 static int kvmppc_get_pvinfo(CPUPPCState *env, struct kvm_ppc_pvinfo *pvinfo)
  {
      PowerPCCPU *cpu = ppc_env_get_cpu(env);
@@ -2442,6 +2455,35 @@
     return cap_spapr_vfio;
 }
 
+int kvmppc_get_cap_large_decr(void)
+{
+    return cap_large_decr;
+}
+
+int kvmppc_enable_cap_large_decr(PowerPCCPU *cpu, int enable)
+{
+    CPUState *cs = CPU(cpu);
+    uint64_t lpcr;
+
+    kvm_get_one_reg(cs, KVM_REG_PPC_LPCR_64, &lpcr);
+    /* Do we need to modify the LPCR? */
+    if (!!(lpcr & LPCR_LD) != !!enable) {
+        if (enable) {
+            lpcr |= LPCR_LD;
+        } else {
+            lpcr &= ~LPCR_LD;
+        }
+        kvm_set_one_reg(cs, KVM_REG_PPC_LPCR_64, &lpcr);
+        kvm_get_one_reg(cs, KVM_REG_PPC_LPCR_64, &lpcr);
+
+        if (!!(lpcr & LPCR_LD) != !!enable) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
 PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void)
 {
     uint32_t host_pvr = mfpvr();