[qemu-xen staging] KVM: fix CPU reset wrt HF2_GIF_MASK

[patchbot@xxxxxxx]

commit 0baa4b445e28f37243e5dc72e7efe32f0c9d7801
Author:     Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
AuthorDate: Thu Jul 23 16:27:01 2020 +0200
Commit:     Eduardo Habkost <ehabkost@xxxxxxxxxx>
CommitDate: Thu Jul 23 15:03:54 2020 -0400

    KVM: fix CPU reset wrt HF2_GIF_MASK
    
    HF2_GIF_MASK is set in env->hflags2 unconditionally on CPU reset
    (see x86_cpu_reset()) but when calling KVM_SET_NESTED_STATE,
    KVM_STATE_NESTED_GIF_SET is only valid for nSVM as e.g. nVMX code
    looks like
    
    if (kvm_state->hdr.vmx.vmxon_pa == -1ull) {
        if (kvm_state->flags & ~KVM_STATE_NESTED_EVMCS)
            return -EINVAL;
    }
    
    Also, when adjusting the environment after KVM_GET_NESTED_STATE we
    need not reset HF2_GIF_MASK on VMX as e.g. x86_cpu_pending_interrupt()
    expects it to be set.
    
    Alternatively, we could've made env->hflags2 SVM-only.
    
    Reported-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
    Fixes: b16c0e20c742 ("KVM: add support for AMD nested live migration")
    Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
    Message-Id: <20200723142701.2521161-1-vkuznets@xxxxxxxxxx>
    Tested-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
    Signed-off-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
---
 target/i386/kvm.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index b8455c89ed..6f18d940a5 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -3877,7 +3877,9 @@ static int kvm_put_nested_state(X86CPU *cpu)
     } else {
         env->nested_state->flags &= ~KVM_STATE_NESTED_GUEST_MODE;
     }
-    if (env->hflags2 & HF2_GIF_MASK) {
+
+    /* Don't set KVM_STATE_NESTED_GIF_SET on VMX as it is illegal */
+    if (cpu_has_svm(env) && (env->hflags2 & HF2_GIF_MASK)) {
         env->nested_state->flags |= KVM_STATE_NESTED_GIF_SET;
     } else {
         env->nested_state->flags &= ~KVM_STATE_NESTED_GIF_SET;
@@ -3919,10 +3921,14 @@ static int kvm_get_nested_state(X86CPU *cpu)
     } else {
         env->hflags &= ~HF_GUEST_MASK;
     }
-    if (env->nested_state->flags & KVM_STATE_NESTED_GIF_SET) {
-        env->hflags2 |= HF2_GIF_MASK;
-    } else {
-        env->hflags2 &= ~HF2_GIF_MASK;
+
+    /* Keep HF2_GIF_MASK set on !SVM as x86_cpu_pending_interrupt() needs it */
+    if (cpu_has_svm(env)) {
+        if (env->nested_state->flags & KVM_STATE_NESTED_GIF_SET) {
+            env->hflags2 |= HF2_GIF_MASK;
+        } else {
+            env->hflags2 &= ~HF2_GIF_MASK;
+        }
     }
 
     return ret;
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#staging