* [Qemu-devel] [PATCH] i386/kvm: add a comment explaining why .feat_names are commented out for Hyper-V feature bits
@ 2018-12-21 14:16 Vitaly Kuznetsov
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From: Vitaly Kuznetsov @ 2018-12-21 14:16 UTC (permalink / raw)
To: Eduardo Habkost
Cc: qemu-devel, Paolo Bonzini, Richard Henderson, Marcelo Tosatti,
Roman Kagan
Hyper-V .feat_names are, unlike hardware features, commented out and it is
not obvious why we do that. Document the current status quo.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
target/i386/cpu.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 677a3bd5fb..18a486c5a0 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -929,6 +929,13 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
*/
.no_autoenable_flags = ~0U,
},
+ /*
+ * .feat_names are commented out for Hyper-V enlightenments because we
+ * don't want to have two different ways for enabling them on QEMU command
+ * line. Some features (e.g. "hyperv_time", "hyperv_vapic", ...) require
+ * enabling several feature bits simultaneously, exposing these bits
+ * individually may just confuse guests.
+ */
[FEAT_HYPERV_EAX] = {
.type = CPUID_FEATURE_WORD,
.feat_names = {
--
2.19.2
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