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Re: [Qemu-devel] [PATCH for-2.12] i386: Don't automatically enable FEAT_
From: |
Wanpeng Li |
Subject: |
Re: [Qemu-devel] [PATCH for-2.12] i386: Don't automatically enable FEAT_KVM_HINTS bits |
Date: |
Wed, 11 Apr 2018 10:00:03 +0800 |
2018-04-11 5:15 GMT+08:00 Eduardo Habkost <address@hidden>:
> 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 <address@hidden>
> Signed-off-by: Eduardo Habkost <address@hidden>
Thanks for the patch, Eduardo!
Tested-by: Wanpeng Li <address@hidden>
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
>