Merge remote-tracking branch 'remotes/ehabkost/tags/x86-next-pull-request' into staging

x86 MDS feature flags

md-clear and mds-no feature flags, for detection and mitigation
of MDS vulnerabilities (CVE-2018-12126, CVE-2018-12127,
CVE-2018-12130, CVE-2019-11091).

# gpg: Signature made Tue 21 May 2019 19:42:43 BST
# gpg:                using RSA key 2807936F984DC5A6
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>" [full]
# Primary key fingerprint: 5A32 2FD5 ABC4 D3DB ACCF  D1AA 2807 936F 984D C5A6

* remotes/ehabkost/tags/x86-next-pull-request:
  target/i386: add MDS-NO feature
  docs: recommend use of md-clear feature on all Intel CPUs
  target/i386: define md-clear bit
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

docs/qemu-cpu-models.texi

@@ -200,6 +200,18 @@ Not included by default in any Intel CPU model.
 Should be explicitly turned on for all Intel CPU models.
 
 Note that not all CPU hardware will support this feature.
+
+@item @code{md-clear}
+
+Required to confirm the MDS (CVE-2018-12126, CVE-2018-12127, CVE-2018-12130,
+CVE-2019-11091) fixes.
+
+Not included by default in any Intel CPU model.
+
+Must be explicitly turned on for all Intel CPU models.
+
+Requires the host CPU microcode to support this feature before it
+can be used for guest CPUs.
 @end table
 
 

target/i386/cpu.c

@@ -1077,7 +1077,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         .feat_names = {
             NULL, NULL, "avx512-4vnniw", "avx512-4fmaps",
             NULL, NULL, NULL, NULL,
-            NULL, NULL, NULL, NULL,
+            NULL, NULL, "md-clear", NULL,
             NULL, NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,
@@ -1184,7 +1184,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         .type = MSR_FEATURE_WORD,
         .feat_names = {
             "rdctl-no", "ibrs-all", "rsba", "skip-l1dfl-vmentry",
-            "ssb-no", NULL, NULL, NULL,
+            "ssb-no", "mds-no", NULL, NULL,
             NULL, NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,