KVM: x86 emulator: define callbacks for using the guest fpu within the emulator

Needed for emulating fpu instructions.

Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 20 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index c00aed12755d..4c0e68226113 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -158,6 +158,8 @@ struct x86_emulate_ops {
         int (*set_dr)(int dr, unsigned long value, struct kvm_vcpu *vcpu);
         int (*set_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
         int (*get_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata);
+        void (*get_fpu)(struct x86_emulate_ctxt *ctxt); /* disables preempt */
+        void (*put_fpu)(struct x86_emulate_ctxt *ctxt); /* reenables preempt */
 };
 
 /* Type, address-of, and value of an instruction's operand. */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 11d692c7018d..5af66515337d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4281,6 +4281,22 @@ static void emulator_set_segment_selector(u16 sel, int seg,
         kvm_set_segment(vcpu, &kvm_seg, seg);
 }
 
+static void emulator_get_fpu(struct x86_emulate_ctxt *ctxt)
+{
+        preempt_disable();
+        kvm_load_guest_fpu(ctxt->vcpu);
+        /*
+         * 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)
+{
+        preempt_enable();
+}
+
 static struct x86_emulate_ops emulate_ops = {
         .read_std            = kvm_read_guest_virt_system,
         .write_std           = kvm_write_guest_virt_system,
@@ -4304,6 +4320,8 @@ static struct x86_emulate_ops emulate_ops = {
         .set_dr              = emulator_set_dr,
         .set_msr             = kvm_set_msr,
         .get_msr             = kvm_get_msr,
+        .get_fpu             = emulator_get_fpu,
+        .put_fpu             = emulator_put_fpu,
 };
 
 static void cache_all_regs(struct kvm_vcpu *vcpu)