KVM: x86 emulator: Allow PM/VM86 switch during task switch

Task switches can switch between Protected Mode and VM86. The current
mode must be updated during the task switch emulation so that the new
segment selectors are interpreted correctly.

In order to let privilege checks succeed, rflags needs to be updated in
the vcpu struct as this causes a CPL update.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ab39d84dee00..53efd597f39e 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1354,7 +1354,11 @@ static unsigned long svm_get_rflags(struct kvm_vcpu *vcpu)
 
 static void svm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
 {
+        unsigned long old_rflags = to_svm(vcpu)->vmcb->save.rflags;
+
         to_svm(vcpu)->vmcb->save.rflags = rflags;
+        if ((old_rflags ^ rflags) & X86_EFLAGS_VM)
+                svm_update_cpl(vcpu);
 }
 
 static void svm_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)