KVM: vmx: update sec exec controls for UMIP iff emulating UMIP

Update SECONDARY_EXEC_DESC for UMIP emulation if and only UMIP
is actually being emulated.  Skipping the VMCS update eliminates
unnecessary VMREAD/VMWRITE when UMIP is supported in hardware,
and on platforms that don't have SECONDARY_VM_EXEC_CONTROL.  The
latter case resolves a bug where KVM would fill the kernel log
with warnings due to failed VMWRITEs on older platforms.

Fixes: 0367f205a3b7 ("KVM: vmx: add support for emulating UMIP")
Cc: stable@vger.kernel.org #4.16
Reported-by: Paolo Zeppegno <pzeppegno@gmail.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Suggested-by: Radim KrÄmář <rkrcmar@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c766880..3f16965 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1494,6 +1494,12 @@ static inline bool cpu_has_vmx_vmfunc(void)
                SECONDARY_EXEC_ENABLE_VMFUNC;
 }
 
+static bool vmx_umip_emulated(void)
+{
+       return vmcs_config.cpu_based_2nd_exec_ctrl &
+               SECONDARY_EXEC_DESC;
+}
+
 static inline bool report_flexpriority(void)
 {
        return flexpriority_enabled;
@@ -4761,14 +4767,16 @@ static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
        else
                hw_cr4 |= KVM_PMODE_VM_CR4_ALWAYS_ON;
 
-       if ((cr4 & X86_CR4_UMIP) && !boot_cpu_has(X86_FEATURE_UMIP)) {
-               vmcs_set_bits(SECONDARY_VM_EXEC_CONTROL,
-                             SECONDARY_EXEC_DESC);
-               hw_cr4 &= ~X86_CR4_UMIP;
-       } else if (!is_guest_mode(vcpu) ||
-                  !nested_cpu_has2(get_vmcs12(vcpu), SECONDARY_EXEC_DESC))
-               vmcs_clear_bits(SECONDARY_VM_EXEC_CONTROL,
+       if (!boot_cpu_has(X86_FEATURE_UMIP) && vmx_umip_emulated()) {
+               if (cr4 & X86_CR4_UMIP) {
+                       vmcs_set_bits(SECONDARY_VM_EXEC_CONTROL,
                                SECONDARY_EXEC_DESC);
+                       hw_cr4 &= ~X86_CR4_UMIP;
+               } else if (!is_guest_mode(vcpu) ||
+                       !nested_cpu_has2(get_vmcs12(vcpu), SECONDARY_EXEC_DESC))
+                       vmcs_clear_bits(SECONDARY_VM_EXEC_CONTROL,
+                                       SECONDARY_EXEC_DESC);
+       }
 
        if (cr4 & X86_CR4_VMXE) {
                /*
@@ -9497,12 +9505,6 @@ static bool vmx_xsaves_supported(void)
                SECONDARY_EXEC_XSAVES;
 }
 
-static bool vmx_umip_emulated(void)
-{
-       return vmcs_config.cpu_based_2nd_exec_ctrl &
-               SECONDARY_EXEC_DESC;
-}
-
 static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx)
 {
        u32 exit_intr_info;