On 10/9/24 10:12, Chao Gao wrote:
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 85ef7452c0..18ba958f46 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1148,8 +1148,8 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
[FEAT_7_2_EDX] = {
.type = CPUID_FEATURE_WORD,
.feat_names = {
- NULL, NULL, NULL, NULL,
- NULL, "mcdt-no", NULL, NULL,
+ "intel-psfd", "ipred-ctrl", "rrsba-ctrl", "ddpd-u",
+ "bhi-ctrl", "mcdt-no", NULL, NULL,
IIUC, these bits depend on "spec-ctrl", which indicates the presence of
IA32_SPEC_CTRL.
Then I think we'd better add dependencies in feature_dependencies[].
(+ kvm mailing list)
Thanks for pointing that out. It seems that any of these bits imply the
presence of IA32_SPEC_CTRL. According to SDM vol4, chapter 2, table 2.2,
the 'Comment' column for the IA32_SPEC_CTRL MSR states:
If any one of the enumeration conditions for defined bit field positions holds.
So, it might be more appropriate to fix KVM's handling of the
IA32_SPEC_CTRL MSR (i.e., guest_has_spec_ctrl_msr()).
what do you think?
You're right, the spec-ctrl CPUID feature covers the IBRS bit of
MSR_IA32_SPEC_CTRL and also the IBPB feature of MSR_IA32_PRED_CMD. It
does not specify the existence of MSR_IA32_SPEC_CTRL.
In practice it's probably not a good idea to omit spec-ctrl when passing
other features to the guest that cover that MSR; but the specification
says it's fine.
Paolo
