kvm: vmx: Don't set hardware IA32_CSTAR MSR on VM-entry

SYSCALL raises #UD in compatibility mode on Intel CPUs, so it's
pointless to load the guest's IA32_CSTAR value into the hardware MSR.

IA32_CSTAR still provides 48 bits of storage on Intel CPUs that have
CPUID.80000001:EDX.LM[bit 29] set, so we cannot remove it from the
vmx_msr_index[] array.

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d754fd0..2084db0 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1382,9 +1382,6 @@ static void setup_msrs(struct vcpu_vmx *vmx)
                index = __find_msr_index(vmx, MSR_LSTAR);
                if (index >= 0)
                        move_msr_up(vmx, index, save_nmsrs++);
-               index = __find_msr_index(vmx, MSR_CSTAR);
-               if (index >= 0)
-                       move_msr_up(vmx, index, save_nmsrs++);
                /*
                 * MSR_STAR is only needed on long mode guests, and only
                 * if efer.sce is enabled.