On Tue, Apr 10, 2018 at 05:13:21PM +0800, Wanpeng Li wrote:
> Hi Eduardo,
> 2018-03-09 22:16 GMT+08:00 Eduardo Habkost <ehabkost@xxxxxxxxxx>:
> > On Fri, Feb 09, 2018 at 06:15:25AM -0800, Wanpeng Li wrote:
> >> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> >>
> >> Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit
> >> to determine if they run on dedicated vCPUs, allowing optimizations such
> >> as usage of qspinlocks.
> >>
> >> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> >> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> >> Cc: Eduardo Habkost <ehabkost@xxxxxxxxxx>
> >> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> >> ---
> >> v1 -> v2:
> >> * add a new feature word
> >>
> >> target/i386/cpu.c | 14 ++++++++++++++
> >> target/i386/cpu.h | 3 +++
> >> target/i386/kvm.c | 4 ++++
> >> 3 files changed, 21 insertions(+)
> >>
> >> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> >> index d70954b..e2974ad 100644
> >> --- a/target/i386/cpu.c
> >> +++ b/target/i386/cpu.c
> >> @@ -358,6 +358,20 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> >> .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EAX,
> >> .tcg_features = TCG_KVM_FEATURES,
> >> },
> >> + [FEAT_KVM_HINTS] = {
> >> + .feat_names = {
> >> + "hint-dedicated", NULL, NULL, NULL,
> >
> > I suggest naming it "kvm-hint-dedicated", to indicate it's
> > KVM-specific.
>
> I found this feature is enabled by default w/o kvm-hint-dedicated
> parameter, any idea how to make it disabled by default?
You mean on "-cpu host", right?
The assumption in most of the 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.
Untested fix below.
Signed-off-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
---
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
--
Eduardo
