From ac34e141596fab70fbe91a396311f80db6cb57c5 Mon Sep 17 00:00:00 2001
From: Jiri Denemark <jdenemar@redhat.com>
Date: Fri, 18 Oct 2019 14:33:19 +0200
Subject: [PATCH] qemu: Drop disabled CPU features unknown to QEMU
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When a CPU definition wants to explicitly disable some features that are
unknown to QEMU, we can safely drop them from the definition before
starting QEMU. Naturally QEMU won't enable such features implicitly.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 src/qemu/qemu_process.c                       | 32 +++++++++++++++++++
 ...-Icelake-Server-pconfig.x86_64-latest.args |  2 +-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 9b7dde66e7..4cf4069d50 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -6047,6 +6047,26 @@ qemuProcessSetupHotpluggableVcpus(virQEMUDriverPtr driver,
 }
 
 
+static bool
+qemuProcessDropUnknownCPUFeatures(const char *name,
+                                  virCPUFeaturePolicy policy,
+                                  void *opaque)
+{
+    const char **features = opaque;
+
+    if (policy != VIR_CPU_FEATURE_DISABLE &&
+        policy != VIR_CPU_FEATURE_FORBID)
+        return true;
+
+    if (virStringListHasString(features, name))
+        return true;
+
+    /* Features unknown to QEMU are implicitly disabled, we can just drop them
+     * from the definition. */
+    return false;
+}
+
+
 static int
 qemuProcessUpdateGuestCPU(virDomainDefPtr def,
                           virQEMUCapsPtr qemuCaps,
@@ -6112,6 +6132,18 @@ qemuProcessUpdateGuestCPU(virDomainDefPtr def,
                                 &def->os.arch) < 0)
         return -1;
 
+    if (ARCH_IS_X86(def->os.arch)) {
+        VIR_AUTOSTRINGLIST features = NULL;
+
+        if (virQEMUCapsGetCPUFeatures(qemuCaps, def->virtType, false, &features) < 0)
+            return -1;
+
+        if (features &&
+            virCPUDefFilterFeatures(def->cpu, qemuProcessDropUnknownCPUFeatures,
+                                    features) < 0)
+            return -1;
+    }
+
     return 0;
 }
 
diff --git a/tests/qemuxml2argvdata/cpu-Icelake-Server-pconfig.x86_64-latest.args b/tests/qemuxml2argvdata/cpu-Icelake-Server-pconfig.x86_64-latest.args
index d6f5a0ad98..88d05a482a 100644
--- a/tests/qemuxml2argvdata/cpu-Icelake-Server-pconfig.x86_64-latest.args
+++ b/tests/qemuxml2argvdata/cpu-Icelake-Server-pconfig.x86_64-latest.args
@@ -13,7 +13,7 @@ QEMU_AUDIO_DRV=none \
 -object secret,id=masterKey0,format=raw,\
 file=/tmp/lib/domain--1-test/master-key.aes \
 -machine pc,accel=kvm,usb=off,dump-guest-core=off \
--cpu Icelake-Server,pconfig=off \
+-cpu Icelake-Server \
 -m 214 \
 -overcommit mem-lock=off \
 -smp 1,sockets=1,cores=1,threads=1 \
-- 
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