Re: [Qemu-devel] [PATCH for-2.12] i386: Don't automatically enable FEAT_KVM_HINTS bits

[Wanpeng Li]

2018-04-11 5:15 GMT+08:00 Eduardo Habkost :
> The assumption in the cpu->max_features code is that anything
> enabled on GET_SUPPORTED_CPUID should be enabled on "-cpu host".
> This shouldn't be the case for FEAT_KVM_HINTS.
>
> This adds a new FeatureWordInfo::no_autoenable_flags field, that
> can be used to prevent FEAT_KVM_HINTS bits to be enabled
> automatically.
>
> Reviewed-by: Paolo Bonzini 
> Signed-off-by: Eduardo Habkost 

Thanks for the patch, Eduardo!
Tested-by: Wanpeng Li 

Regards,
Wanpeng Li

> ---
>  target/i386/cpu.c | 10 +-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 1a6b082b6f..a20fe26573 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -295,6 +295,8 @@ typedef struct FeatureWordInfo {
>  uint32_t tcg_features; /* Feature flags supported by TCG */
>  uint32_t unmigratable_flags; /* Feature flags known to be unmigratable */
>  uint32_t migratable_flags; /* Feature flags known to be migratable */
> +/* Features that shouldn't be auto-enabled by "-cpu host" */
> +uint32_t no_autoenable_flags;
>  } FeatureWordInfo;
>
>  static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> @@ -400,6 +402,11 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] 
> = {
>  },
>  .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX,
>  .tcg_features = TCG_KVM_FEATURES,
> +/*
> + * KVM hints aren't auto-enabled by -cpu host, they need to be
> + * explicitly enabled in the command-line.
> + */
> +.no_autoenable_flags = ~0U,
>  },
>  [FEAT_HYPERV_EAX] = {
>  .feat_names = {
> @@ -4062,7 +4069,8 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error 
> **errp)
>   */
>  env->features[w] |=
>  x86_cpu_get_supported_feature_word(w, cpu->migratable) &
> -~env->user_features[w];
> +~env->user_features[w] & \
> +~feature_word_info[w].no_autoenable_flags;
>  }
>  }
>
> --
> 2.14.3
>

[Qemu-devel] [PATCH for-2.12] i386: Don't automatically enable FEAT_KVM_HINTS bits

[Eduardo Habkost]

The assumption in the cpu->max_features code is that anything
enabled on GET_SUPPORTED_CPUID should be enabled on "-cpu host".
This shouldn't be the case for FEAT_KVM_HINTS.

This adds a new FeatureWordInfo::no_autoenable_flags field, that
can be used to prevent FEAT_KVM_HINTS bits to be enabled
automatically.

Reviewed-by: Paolo Bonzini 
Signed-off-by: Eduardo Habkost 
---
 target/i386/cpu.c | 10 +-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 1a6b082b6f..a20fe26573 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -295,6 +295,8 @@ typedef struct FeatureWordInfo {
 uint32_t tcg_features; /* Feature flags supported by TCG */
 uint32_t unmigratable_flags; /* Feature flags known to be unmigratable */
 uint32_t migratable_flags; /* Feature flags known to be migratable */
+/* Features that shouldn't be auto-enabled by "-cpu host" */
+uint32_t no_autoenable_flags;
 } FeatureWordInfo;
 
 static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
@@ -400,6 +402,11 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
 },
 .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX,
 .tcg_features = TCG_KVM_FEATURES,
+/*
+ * KVM hints aren't auto-enabled by -cpu host, they need to be
+ * explicitly enabled in the command-line.
+ */
+.no_autoenable_flags = ~0U,
 },
 [FEAT_HYPERV_EAX] = {
 .feat_names = {
@@ -4062,7 +4069,8 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error 
**errp)
  */
 env->features[w] |=
 x86_cpu_get_supported_feature_word(w, cpu->migratable) &
-~env->user_features[w];
+~env->user_features[w] & \
+~feature_word_info[w].no_autoenable_flags;
 }
 }
 
-- 
2.14.3