TCG uses the AMD cpu which warns when we use hyperthreading. Disable
the warning for TCG since it is not necessary.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
---
 target/i386/cpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 7aa762245a..66242893b6 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -3647,7 +3647,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
      * NOTE: the following code has to follow qemu_init_vcpu(). Otherwise
      * cs->nr_threads hasn't be populated yet and the checking is incorrect.
      */
-    if (!IS_INTEL_CPU(env) && cs->nr_threads > 1 && !ht_warned) {
+    if (!IS_INTEL_CPU(env) && cs->nr_threads > 1 && !ht_warned && kvm_enabled()) {
         error_report("AMD CPU doesn't support hyperthreading. Please configure"
                      " -smp options properly.");
         ht_warned = true;
-- 
2.11.0

On 29/03/2017 06:32, Pranith Kumar wrote:
> TCG uses the AMD cpu which warns when we use hyperthreading. Disable
> the warning for TCG since it is not necessary.
> 
> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
> ---
>  target/i386/cpu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 7aa762245a..66242893b6 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -3647,7 +3647,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>       * NOTE: the following code has to follow qemu_init_vcpu(). Otherwise
>       * cs->nr_threads hasn't be populated yet and the checking is incorrect.
>       */
> -    if (!IS_INTEL_CPU(env) && cs->nr_threads > 1 && !ht_warned) {
> +    if (!IS_INTEL_CPU(env) && cs->nr_threads > 1 && !ht_warned && kvm_enabled()) {
>          error_report("AMD CPU doesn't support hyperthreading. Please configure"
>                       " -smp options properly.");
>          ht_warned = true;

AMD Zen supports hyperthreading.  We should check if it uses the same
CPUID leaves and drop the if completely (but not in 2.9).

Paolo

On Wed, Mar 29, 2017 at 10:31:13AM +0200, Paolo Bonzini wrote:
> On 29/03/2017 06:32, Pranith Kumar wrote:
> > TCG uses the AMD cpu which warns when we use hyperthreading. Disable
> > the warning for TCG since it is not necessary.
> > 
> > Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
> > ---
> >  target/i386/cpu.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index 7aa762245a..66242893b6 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -3647,7 +3647,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
> >       * NOTE: the following code has to follow qemu_init_vcpu(). Otherwise
> >       * cs->nr_threads hasn't be populated yet and the checking is incorrect.
> >       */
> > -    if (!IS_INTEL_CPU(env) && cs->nr_threads > 1 && !ht_warned) {
> > +    if (!IS_INTEL_CPU(env) && cs->nr_threads > 1 && !ht_warned && kvm_enabled()) {
> >          error_report("AMD CPU doesn't support hyperthreading. Please configure"
> >                       " -smp options properly.");
> >          ht_warned = true;
> 
> AMD Zen supports hyperthreading.  We should check if it uses the same
> CPUID leaves and drop the if completely (but not in 2.9).

AMD's CPUID specification documents the same bit
(CPUID[1].EDX[bit 28]) as "HTT: hyper-threading technology".

However:

* Their Extended Method for topology enumeration
  ignores HTT and CmpLegacy, and has contiguous APIC IDs assigned
  for each core[1]. I don't know if their Extended Method is
  compatible[2] with the topology information we expose when
  nr_threads>1. (I expect it to be compatible, but I'm not sure.)
* Their docs for the Legacy Method for CPU topology enumeration
  don't mention what to do if CmpLegacy=0, HTT=1.

[1] The APIC ID formula is:
    LocalApicId[proc=i, core=j] = (OFFSET_IDX + i) * MNC + j
[2] By compatible, I mean placing the cores/threads at the right
    physical processor, at least (even if it treats each thread
    as a separate core).

-- 
Eduardo