i386: Define the Virt SSBD MSR and handling of it (CVE-2018-3639)

"Some AMD processors only support a non-architectural means of enabling
speculative store bypass disable (SSBD).  To allow a simplified view of
this to a guest, an architectural definition has been created through a new
CPUID bit, 0x80000008_EBX[25], and a new MSR, 0xc001011f.  With this, a
hypervisor can virtualize the existence of this definition and provide an
architectural method for using SSBD to a guest.

Add the new CPUID feature, the new MSR and update the existing SSBD
support to use this MSR when present." (from x86/speculation: Add virtualized
speculative store bypass disable support in Linux).

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20180521215424.13520-4-berrange@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/target/i386/machine.c b/target/i386/machine.c
index fd99c0bbb4..4d98d367c1 100644
--- a/target/i386/machine.c
+++ b/target/i386/machine.c
@@ -916,6 +916,25 @@ static const VMStateDescription vmstate_msr_intel_pt = {
     }
 };
 
+static bool virt_ssbd_needed(void *opaque)
+{
+    X86CPU *cpu = opaque;
+    CPUX86State *env = &cpu->env;
+
+    return env->virt_ssbd != 0;
+}
+
+static const VMStateDescription vmstate_msr_virt_ssbd = {
+    .name = "cpu/virt_ssbd",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = virt_ssbd_needed,
+    .fields = (VMStateField[]){
+        VMSTATE_UINT64(env.virt_ssbd, X86CPU),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 VMStateDescription vmstate_x86_cpu = {
     .name = "cpu",
     .version_id = 12,
@@ -1039,6 +1058,7 @@ VMStateDescription vmstate_x86_cpu = {
         &vmstate_spec_ctrl,
         &vmstate_mcg_ext_ctl,
         &vmstate_msr_intel_pt,
+        &vmstate_msr_virt_ssbd,
         NULL
     }
 };