KVM: VMX: Add lazy FPU support for VT

Only save/restore the FPU host state when the guest is actually using the
FPU.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index 0960811..5a2a68d 100644 (file)
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -101,6 +101,13 @@ static inline int is_page_fault(u32 intr_info)
                (INTR_TYPE_EXCEPTION | PF_VECTOR | INTR_INFO_VALID_MASK);
 }
 
+static inline int is_no_device(u32 intr_info)
+{
+       return (intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VECTOR_MASK |
+                            INTR_INFO_VALID_MASK)) ==
+               (INTR_TYPE_EXCEPTION | NM_VECTOR | INTR_INFO_VALID_MASK);
+}
+
 static inline int is_external_interrupt(u32 intr_info)
 {
        return (intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VALID_MASK))
@@ -216,6 +223,16 @@ static void vmcs_write64(unsigned long field, u64 value)
 #endif
 }
 
+static void vmcs_clear_bits(unsigned long field, u32 mask)
+{
+       vmcs_writel(field, vmcs_readl(field) & ~mask);
+}
+
+static void vmcs_set_bits(unsigned long field, u32 mask)
+{
+       vmcs_writel(field, vmcs_readl(field) | mask);
+}
+
 /*
  * Switches to specified vcpu, until a matching vcpu_put(), but assumes
  * vcpu mutex is already taken.
@@ -833,6 +850,11 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
        }
 #endif
 
+       if (!(cr0 & CR0_TS_MASK)) {
+               vcpu->fpu_active = 1;
+               vmcs_clear_bits(EXCEPTION_BITMAP, CR0_TS_MASK);
+       }
+
        vmcs_writel(CR0_READ_SHADOW, cr0);
        vmcs_writel(GUEST_CR0,
                    (cr0 & ~KVM_GUEST_CR0_MASK) | KVM_VM_CR0_ALWAYS_ON);
@@ -842,6 +864,12 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 {
        vmcs_writel(GUEST_CR3, cr3);
+
+       if (!(vcpu->cr0 & CR0_TS_MASK)) {
+               vcpu->fpu_active = 0;
+               vmcs_set_bits(GUEST_CR0, CR0_TS_MASK);
+               vmcs_set_bits(EXCEPTION_BITMAP, 1 << NM_VECTOR);
+       }
 }
 
 static void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
@@ -1368,6 +1396,15 @@ static int handle_exception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
                asm ("int $2");
                return 1;
        }
+
+       if (is_no_device(intr_info)) {
+               vcpu->fpu_active = 1;
+               vmcs_clear_bits(EXCEPTION_BITMAP, 1 << NM_VECTOR);
+               if (!(vcpu->cr0 & CR0_TS_MASK))
+                       vmcs_clear_bits(GUEST_CR0, CR0_TS_MASK);
+               return 1;
+       }
+
        error_code = 0;
        rip = vmcs_readl(GUEST_RIP);
        if (intr_info & INTR_INFO_DELIEVER_CODE_MASK)
@@ -1556,7 +1593,11 @@ static int handle_cr(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
                break;
        case 2: /* clts */
                vcpu_load_rsp_rip(vcpu);
-               set_cr0(vcpu, vcpu->cr0 & ~CR0_TS_MASK);
+               vcpu->fpu_active = 1;
+               vmcs_clear_bits(EXCEPTION_BITMAP, 1 << NM_VECTOR);
+               vmcs_clear_bits(GUEST_CR0, CR0_TS_MASK);
+               vcpu->cr0 &= ~CR0_TS_MASK;
+               vmcs_writel(CR0_READ_SHADOW, vcpu->cr0);
                skip_emulated_instruction(vcpu);
                return 1;
        case 1: /*mov from cr*/
@@ -1806,8 +1847,14 @@ again:
        if (vcpu->guest_debug.enabled)
                kvm_guest_debug_pre(vcpu);
 
-       fx_save(vcpu->host_fx_image);
-       fx_restore(vcpu->guest_fx_image);
+       if (vcpu->fpu_active) {
+               fx_save(vcpu->host_fx_image);
+               fx_restore(vcpu->guest_fx_image);
+       }
+       /*
+        * Loading guest fpu may have cleared host cr0.ts
+        */
+       vmcs_writel(HOST_CR0, read_cr0());
 
 #ifdef CONFIG_X86_64
        if (is_long_mode(vcpu)) {
@@ -1965,8 +2012,11 @@ again:
        }
 #endif
 
-       fx_save(vcpu->guest_fx_image);
-       fx_restore(vcpu->host_fx_image);
+       if (vcpu->fpu_active) {
+               fx_save(vcpu->guest_fx_image);
+               fx_restore(vcpu->host_fx_image);
+       }
+
        vcpu->interrupt_window_open = (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & 3) == 0;
 
        asm ("mov %0, %%ds; mov %0, %%es" : : "r"(__USER_DS));
@@ -2078,6 +2128,7 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu)
        vmcs_clear(vmcs);
        vcpu->vmcs = vmcs;
        vcpu->launched = 0;
+       vcpu->fpu_active = 1;
 
        return 0;