i386: Disable TOPOEXT by default on "-cpu host"

Enabling TOPOEXT is always allowed, but it can't be enabled
blindly by "-cpu host" because it may make guests crash if the
rest of the cache topology information isn't provided or isn't
consistent.

This addresses the bug reported at:
https://bugzilla.redhat.com/show_bug.cgi?id=1613277

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20180809221852.15285-1-ehabkost@redhat.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
(cherry picked from commit 7210a02c58572b2686a3a8d610c6628f87864aed)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 723e02221e5e8d9e23fed67481c6de87ba0d2f0e..3ac627978f3e967e5557c1db256ae255dde6f514 100644 (file)
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -849,6 +849,12 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         },
         .cpuid_eax = 0x80000001, .cpuid_reg = R_ECX,
         .tcg_features = TCG_EXT3_FEATURES,
+        /*
+         * TOPOEXT is always allowed but can't be enabled blindly by
+         * "-cpu host", as it requires consistent cache topology info
+         * to be provided so it doesn't confuse guests.
+         */
+        .no_autoenable_flags = CPUID_EXT3_TOPOEXT,
     },
     [FEAT_C000_0001_EDX] = {
         .feat_names = {