Revert "x86/svm: Add code to clobber the RSB on VM exit"

CVE-2017-5753 (revert embargoed)
CVE-2017-5715 (revert embargoed)

This reverts commit b554560f.
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/x86/kvm/svm.c

@@ -3932,8 +3932,6 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
 			wrmsrl(MSR_IA32_SPEC_CTRL, FEATURE_ENABLE_IBRS);
 	}
 
-	stuff_RSB();
-
 #ifdef CONFIG_X86_64
 	wrmsrl(MSR_GS_BASE, svm->host.gs_base);
 #else