4 files changed, 27 insertions, 2 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5a1faf3f043e..f4a555beef19 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -401,6 +401,7 @@ struct kvm_vcpu_arch {
         struct kvm_mmu_memory_cache mmu_page_header_cache;
 
         struct fpu guest_fpu;
+        bool eager_fpu;
         u64 xcr0;
         u64 guest_supported_xcr0;
         u32 guest_xstate_size;
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 59b69f6a2844..1d08ad3582d0 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -16,6 +16,8 @@
 #include <linux/module.h>
 #include <linux/vmalloc.h>
 #include <linux/uaccess.h>
+#include <asm/i387.h> /* For use_eager_fpu.  Ugh! */
+#include <asm/fpu-internal.h> /* For use_eager_fpu.  Ugh! */
 #include <asm/user.h>
 #include <asm/xsave.h>
 #include "cpuid.h"
@@ -95,6 +97,8 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
         if (best && (best->eax & (F(XSAVES) | F(XSAVEC))))
                 best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
 
+        vcpu->arch.eager_fpu = guest_cpuid_has_mpx(vcpu);
+
         /*
          * The existing code assumes virtual address is 48-bit in the canonical
          * address checks; exit if it is ever changed.
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index c3b1ad9fca81..496b3695d3d3 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -117,4 +117,12 @@ static inline bool guest_cpuid_has_rtm(struct kvm_vcpu *vcpu)
         best = kvm_find_cpuid_entry(vcpu, 7, 0);
         return best && (best->ebx & bit(X86_FEATURE_RTM));
 }
+
+static inline bool guest_cpuid_has_mpx(struct kvm_vcpu *vcpu)
+{
+        struct kvm_cpuid_entry2 *best;
+
+        best = kvm_find_cpuid_entry(vcpu, 7, 0);
+        return best && (best->ebx & bit(X86_FEATURE_MPX));
+}
 #endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5f3818846465..ea306adbbc13 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7060,7 +7060,9 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
         fpu_save_init(&vcpu->arch.guest_fpu);
         __kernel_fpu_end();
         ++vcpu->stat.fpu_reload;
-        kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
+        if (!vcpu->arch.eager_fpu)
+                kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
+
         trace_kvm_fpu(0);
 }
 
@@ -7076,11 +7078,21 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
 struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
                                                 unsigned int id)
 {
+        struct kvm_vcpu *vcpu;
+
         if (check_tsc_unstable() && atomic_read(&kvm->online_vcpus) != 0)
                 printk_once(KERN_WARNING
                 "kvm: SMP vm created on host with unstable TSC; "
                 "guest TSC will not be reliable\n");
-        return kvm_x86_ops->vcpu_create(kvm, id);
+
+        vcpu = kvm_x86_ops->vcpu_create(kvm, id);
+
+        /*
+         * Activate fpu unconditionally in case the guest needs eager FPU.  It will be
+         * deactivated soon if it doesn't.
+         */
+        kvm_x86_ops->fpu_activate(vcpu);
+        return vcpu;
 }
 
 int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)