Re: [Qemu-devel] [PATCH] tcg/i386: Display AMD HT warning only for KVM
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 > > --- > > 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
Re: [Qemu-devel] [PATCH] tcg/i386: Display AMD HT warning only for KVM
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 > --- > 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
[Qemu-devel] [PATCH] tcg/i386: Display AMD HT warning only for KVM
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 --- 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