[PATCH 4/8] x86/kvm: Remove host CR0.TS manipulation

[Andy Lutomirski]

Now that x86 always uses eager fpu switching on the host, there's no
need for KVM to manipulate the host's CR0.TS.

This should be both simpler and faster.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
 arch/x86/kvm/vmx.c | 12 ++++--------
 arch/x86/kvm/x86.c |  5 -----
 2 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index cf1b16dbc98a..531c44633190 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2144,12 +2144,6 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
 #endif
 	if (vmx->host_state.msr_host_bndcfgs)
 		wrmsrl(MSR_IA32_BNDCFGS, vmx->host_state.msr_host_bndcfgs);
-	/*
-	 * If the FPU is not active (through the host task or
-	 * the guest vcpu), then restore the cr0.TS bit.
-	 */
-	if (!fpregs_active() && !vmx->vcpu.guest_fpu_loaded)
-		stts();
 	load_gdt(this_cpu_ptr(&host_gdt));
 }
 
@@ -4871,9 +4865,11 @@ static void vmx_set_constant_host_state(struct vcpu_vmx *vmx)
 	u32 low32, high32;
 	unsigned long tmpl;
 	struct desc_ptr dt;
-	unsigned long cr4;
+	unsigned long cr0, cr4;
 
-	vmcs_writel(HOST_CR0, read_cr0() & ~X86_CR0_TS);  /* 22.2.3 */
+	cr0 = read_cr0();
+	WARN_ON(cr0 & X86_CR0_TS);
+	vmcs_writel(HOST_CR0, cr0);  /* 22.2.3 */
 	vmcs_writel(HOST_CR3, read_cr3());  /* 22.2.3  FIXME: shadow tables */
 
 	/* Save the most likely value for this task's CR4 in the VMCS. */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d5700263dad2..123d428d319a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5060,11 +5060,6 @@ static void emulator_get_fpu(struct x86_emulate_ctxt *ctxt)
 {
 	preempt_disable();
 	kvm_load_guest_fpu(emul_to_vcpu(ctxt));
-	/*
-	 * CR0.TS may reference the host fpu state, not the guest fpu state,
-	 * so it may be clear at this point.
-	 */
-	clts();
 }
 
 static void emulator_put_fpu(struct x86_emulate_ctxt *ctxt)
-- 
2.7.4