Re: [Qemu-devel] [PATCH] tcg/i386: Do not display HT warning for TCG

[Pranith Kumar]

On Wed, Apr 19, 2017 at 3:54 PM, Pranith Kumar <address@hidden> wrote:
> When we enable hyperthreading (using threads smp argument), we warn
> the user if the cpu is an AMD cpu. This does not make sense on TCG and
> is also obsolete now that AMD Ryzen support hyperthreading.
>
> Fix this by adding CPUID_HT bit to the TCG features and explicitly
> checking this bit in the cpuid.
>
> Signed-off-by: Pranith Kumar <address@hidden>
> ---
>  target/i386/cpu.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 13c0985f11..f34bb5ead7 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -202,12 +202,12 @@ static void x86_cpu_vendor_words2str(char *dst, 
> uint32_t vendor1,
>  #define TCG_FEATURES (CPUID_FP87 | CPUID_PSE | CPUID_TSC | CPUID_MSR | \
>            CPUID_PAE | CPUID_MCE | CPUID_CX8 | CPUID_APIC | CPUID_SEP | \
>            CPUID_MTRR | CPUID_PGE | CPUID_MCA | CPUID_CMOV | CPUID_PAT | \
> -          CPUID_PSE36 | CPUID_CLFLUSH | CPUID_ACPI | CPUID_MMX | \
> +          CPUID_PSE36 | CPUID_CLFLUSH | CPUID_ACPI | CPUID_MMX | CPUID_HT | \
>            CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS | CPUID_DE)
>            /* partly implemented:
>            CPUID_MTRR, CPUID_MCA, CPUID_CLFLUSH (needed for Win64) */
>            /* missing:
> -          CPUID_VME, CPUID_DTS, CPUID_SS, CPUID_HT, CPUID_TM, CPUID_PBE */
> +          CPUID_VME, CPUID_DTS, CPUID_SS, CPUID_TM, CPUID_PBE */
>  #define TCG_EXT_FEATURES (CPUID_EXT_SSE3 | CPUID_EXT_PCLMULQDQ | \
>            CPUID_EXT_MONITOR | CPUID_EXT_SSSE3 | CPUID_EXT_CX16 | \
>            CPUID_EXT_SSE41 | CPUID_EXT_SSE42 | CPUID_EXT_POPCNT | \
> @@ -3643,7 +3643,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error 
> **errp)
>
>      qemu_init_vcpu(cs);
>
> -    /* Only Intel CPUs support hyperthreading. Even though QEMU fixes this
> +    /* Only some CPUs support hyperthreading. Even though QEMU fixes this
>       * issue by adjusting CPUID_0000_0001_EBX and CPUID_8000_0008_ECX
>       * based on inputs (sockets,cores,threads), it is still better to gives
>       * users a warning.
> @@ -3651,8 +3651,8 @@ 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) {
> -        error_report("AMD CPU doesn't support hyperthreading. Please 
> configure"
> +    if ((env->features[FEAT_1_EDX] & CPUID_HT) && (cs->nr_threads > 1) && 
> !ht_warned) {

I missed a '!' here. We need to warn if CPUID_HT is not set. But I see
that it is not being set even on HT enabled processors (i7-3770). How
do I test for it?

-- 
Pranith