[Qemu-devel] [PATCH v3 7/9] target/i386: Support multi-dies when host doesn't support CPUID.1F

[Like Xu <like.xu@linux.intel.com>]

In guest CPUID generation process, the cpuid_min_level would be adjusted to
the maximum passed value for basic CPUID configuration and it should not be
restricted by the limited value returned from cpu_x86_cpuid(). After the basic
cpu_x86_cpuid() loop is finished, the cpuid_0_entry.eax needs to be configured
again by the last adjusted cpuid_min_level value.

If a user wants to expose CPUID.1F by passing dies > 1 for any reason without
host support, a per-cpu smp topology warning will appear but it's not blocked.

Signed-off-by: Like Xu <like.xu@linux.intel.com>
---
 target/i386/kvm.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 9b4da9b265..8bf1604d2b 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -931,12 +931,12 @@ int kvm_arch_init_vcpu(CPUState *cs)
     struct kvm_cpuid_entry2 *c;
     uint32_t signature[3];
     int kvm_base = KVM_CPUID_SIGNATURE;
-    int r;
+    int r, cpuid_0_entry, cpuid_min_level;
     Error *local_err = NULL;
 
     memset(&cpuid_data, 0, sizeof(cpuid_data));
 
-    cpuid_i = 0;
+    cpuid_i = cpuid_0_entry = cpuid_min_level = 0;
 
     r = kvm_arch_set_tsc_khz(cs);
     if (r < 0) {
@@ -1050,6 +1050,12 @@ int kvm_arch_init_vcpu(CPUState *cs)
 
     cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
 
+    /* Allow 0x1f setting regardless of kvm support if nr_dies > 1 */
+    if (limit < 0x1f && env->nr_dies > 1 && cpu->enable_cpuid_0x1f) {
+        limit = env->cpuid_level = env->cpuid_min_level = 0x1f;
+        warn_report("CPU topology: the CPUID.1F isn't supported on the host.");
+    }
+
     for (i = 0; i <= limit; i++) {
         if (cpuid_i == KVM_MAX_CPUID_ENTRIES) {
             fprintf(stderr, "unsupported level value: 0x%x\n", limit);
@@ -1151,8 +1157,22 @@ int kvm_arch_init_vcpu(CPUState *cs)
             cpu_x86_cpuid(env, i, 0, &c->eax, &c->ebx, &c->ecx, &c->edx);
             break;
         }
+
+        /* Remember the index of cpuid.0 leaf for reconfiguration. */
+        cpuid_0_entry = (i == 0) ? (cpuid_i - 1) : cpuid_0_entry;
+
+        /* Adjust cpuid_min_level to the maximum index of valid basic cpuids. */
+        cpuid_min_level =
+                ((c->eax | c->ebx | c->ecx | c->edx | c->flags | c->index) &&
+                                (i > cpuid_min_level)) ? i : cpuid_min_level;
     }
 
+    env->cpuid_level = env->cpuid_min_level = cpuid_min_level;
+
+    /* Reconfigure cpuid_0_eax value to follow CPUID.0 instruction spec.*/
+    c = &cpuid_data.entries[cpuid_0_entry];
+    cpu_x86_cpuid(env, 0, 0, &c->eax, &c->ebx, &c->ecx, &c->edx);
+
     if (limit >= 0x0a) {
         uint32_t eax, edx;
 
-- 
2.21.0