[PATCH] targer/i386/cpu: Fix CPUID_HT exposure

[PATCH] targer/i386/cpu: Fix CPUID_HT exposure

[Xiaoyao Li]

When explicitly booting a multiple vcpus vm with "-cpu +ht", it gets
warning of

  warning: host doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]

Make CPUID_HT as supported unconditionally can resolve the warning.
However it introduces another issue that it also expose CPUID_HT to
guest when "-cpu host/max" with only 1 vcpu. To fix this, need mark
CPUID_HT as the no_autoenable_flags.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 target/i386/cpu.c     | 1 +
 target/i386/kvm/kvm.c | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index cec5d2b7b65e..32c077455f04 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -778,6 +778,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         },
         .cpuid = {.eax = 1, .reg = R_EDX, },
         .tcg_features = TCG_FEATURES,
+        .no_autoenable_flags = CPUID_HT,
     },
     [FEAT_1_ECX] = {
         .type = CPUID_FEATURE_WORD,
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index f6c7f7e26869..ab72bcdfad13 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -373,6 +373,8 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
     if (function == 1 && reg == R_EDX) {
         /* KVM before 2.6.30 misreports the following features */
         ret |= CPUID_MTRR | CPUID_PAT | CPUID_MCE | CPUID_MCA;
+        /* KVM never reports CPUID_HT but QEMU can support when vcpus > 1 */
+        ret |= CPUID_HT;
     } else if (function == 1 && reg == R_ECX) {
         /* We can set the hypervisor flag, even if KVM does not return it on
          * GET_SUPPORTED_CPUID

base-commit: cea3ea670fe265421131aad90c36fbb87bc4d206
-- 
2.34.1

Re: [PATCH] targer/i386/cpu: Fix CPUID_HT exposure

[Paolo Bonzini]

Queued, thanks.

Paolo

Re: [PATCH] targer/i386/cpu: Fix CPUID_HT exposure

[Farrah Chen]

On 2023-10-10 at 02:05:39 -0400, Xiaoyao Li wrote:
> When explicitly booting a multiple vcpus vm with "-cpu +ht", it gets
> warning of
> 
>   warning: host doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]
> 
> Make CPUID_HT as supported unconditionally can resolve the warning.
> However it introduces another issue that it also expose CPUID_HT to
> guest when "-cpu host/max" with only 1 vcpu. To fix this, need mark
> CPUID_HT as the no_autoenable_flags.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  target/i386/cpu.c     | 1 +
>  target/i386/kvm/kvm.c | 2 ++
>  2 files changed, 3 insertions(+)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index cec5d2b7b65e..32c077455f04 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -778,6 +778,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
>          },
>          .cpuid = {.eax = 1, .reg = R_EDX, },
>          .tcg_features = TCG_FEATURES,
> +        .no_autoenable_flags = CPUID_HT,
>      },
>      [FEAT_1_ECX] = {
>          .type = CPUID_FEATURE_WORD,
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index f6c7f7e26869..ab72bcdfad13 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -373,6 +373,8 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
>      if (function == 1 && reg == R_EDX) {
>          /* KVM before 2.6.30 misreports the following features */
>          ret |= CPUID_MTRR | CPUID_PAT | CPUID_MCE | CPUID_MCA;
> +        /* KVM never reports CPUID_HT but QEMU can support when vcpus > 1 */
> +        ret |= CPUID_HT;
>      } else if (function == 1 && reg == R_ECX) {
>          /* We can set the hypervisor flag, even if KVM does not return it on
>           * GET_SUPPORTED_CPUID

Tested-by: Farrah Chen <farrah.chen@intel.com>

> 
> base-commit: cea3ea670fe265421131aad90c36fbb87bc4d206
> -- 
> 2.34.1
> 
>