kvm/fpu: Enable eager restore kvm FPU for MPX

[ Upstream commit c447e76b4cabb49ddae8e49c5758f031f35d55fb ]

The MPX feature requires eager KVM FPU restore support. We have verified
that MPX cannot work correctly with the current lazy KVM FPU restore
mechanism. Eager KVM FPU restore should be enabled if the MPX feature is
exposed to VM.

Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
Signed-off-by: Liang Li <liang.z.li@intel.com>
[Also activate the FPU on AMD processors. - Paolo]
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3e8717f6fb337b192f5b78e1586aea8b4948d2b8..6c0709ff2f386bb1b23460959d5b6fce4aa900b6 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -393,6 +393,7 @@ 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 88f92014ba6be27cd4d0cea4593b42af0a5a0bc7..81c6d541d98a7f6e17cc7991da02c86512c8363a 100644 (file)
--- 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"
@@ -88,6 +90,8 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
                        xstate_required_size(vcpu->arch.xcr0);
        }
 
+       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 4452eedfaedd0a4849b54d4137edd5e85b24ae46..9bec2b8cdcedcb91b4739041e7710bb057147f80 100644 (file)
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -111,4 +111,12 @@ 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 f764dd1b23e800c917da18023dc3ab5530893623..0bb431c3f74e1192501ac967e4504c8f6c06a343 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6993,7 +6993,9 @@ 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);
 }
 
@@ -7009,11 +7011,21 @@ 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)