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

[Eduardo Habkost <ehabkost@redhat.com>]

On Wed, Jun 19, 2019 at 04:15:46PM -0300, Eduardo Habkost wrote:
> On Wed, Jun 12, 2019 at 04:41:02PM +0800, Like Xu wrote:
> > 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>
> 
> This code doesn't look at host CPUID at all, as far as I can see.
> Isn't it simpler to just make cpuid_x86_cpuid() return the
> correct data?

I suggest the following change instead.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 target/i386/cpu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 6db38e145b..d05a224092 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5152,6 +5152,10 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
             x86_cpu_adjust_level(cpu, &cpu->env.cpuid_min_level, 0x14);
         }
 
+        if (env->nr_dies > 1) {
+            x86_cpu_adjust_level(cpu, &env->cpuid_min_level, 0x1F);
+        }
+
         /* SVM requires CPUID[0x8000000A] */
         if (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_SVM) {
             x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000000A);
-- 
2.18.0.rc1.1.g3f1ff2140