[PATCH RFC 3/5] x86,fpu: add kernel fpu argument to __kernel_fpu_begin

[riel]

From: Rik van Riel <r...@redhat.com>

Most kernel FPU contexts are transient, but a KVM VCPU context
persists.  Add a kernel FPU argument to __kernel_fpu_begin, so
we can know whether or not the KVM VCPU context got clobbered
by another kernel FPU context.

Signed-off-by: Rik van Riel <r...@redhat.com>
---
 arch/x86/include/asm/efi.h     | 2 +-
 arch/x86/include/asm/fpu/api.h | 2 +-
 arch/x86/kernel/fpu/core.c     | 6 +++---
 arch/x86/kvm/x86.c             | 8 ++++++--
 4 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index d0bb76d81402..603d2cdd6b82 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -71,7 +71,7 @@ struct efi_scratch {
 ({                                                                     \
        efi_sync_low_kernel_mappings();                                 \
        preempt_disable();                                              \
-       __kernel_fpu_begin();                                           \
+       __kernel_fpu_begin(NULL);                                       \
                                                                        \
        if (efi_scratch.use_pgd) {                                      \
                efi_scratch.prev_cr3 = read_cr3();                      \
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index edd7dc7ae4f7..f6704edf9904 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -20,7 +20,7 @@
  * All other cases use kernel_fpu_begin/end() which disable preemption
  * during kernel FPU usage.
  */
-extern void __kernel_fpu_begin(void);
+extern void __kernel_fpu_begin(struct fpu *fpu);
 extern void __kernel_fpu_end(void);
 extern void kernel_fpu_begin(void);
 extern void kernel_fpu_end(void);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index c4350f188be1..537eb65b6ae6 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -110,7 +110,7 @@ bool irq_fpu_usable(void)
 }
 EXPORT_SYMBOL(irq_fpu_usable);
 
-void __kernel_fpu_begin(void)
+void __kernel_fpu_begin(struct fpu *kernelfpu)
 {
        struct fpu *fpu = &current->thread.fpu;
 
@@ -118,7 +118,7 @@ void __kernel_fpu_begin(void)
 
        kernel_fpu_disable();
 
-       this_cpu_write(fpu_fpregs_owner_ctx, NULL);
+       this_cpu_write(fpu_fpregs_owner_ctx, kernelfpu);
 
        if (fpu->fpregs_active) {
                /*
@@ -150,7 +150,7 @@ EXPORT_SYMBOL(__kernel_fpu_end);
 void kernel_fpu_begin(void)
 {
        preempt_disable();
-       __kernel_fpu_begin();
+       __kernel_fpu_begin(NULL);
 }
 EXPORT_SYMBOL_GPL(kernel_fpu_begin);
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 699f8726539a..55c82d066d3a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7332,6 +7332,8 @@ static void fx_init(struct kvm_vcpu *vcpu)
 
 void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
 {
+       struct fpu *fpu;
+
        if (vcpu->guest_fpu_loaded)
                return;
 
@@ -7340,9 +7342,11 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
         * and assume host would use all available bits.
         * Guest xcr0 would be loaded later.
         */
+       fpu = &vcpu->arch.guest_fpu;
+
        vcpu->guest_fpu_loaded = 1;
-       __kernel_fpu_begin();
-       __copy_kernel_to_fpregs(&vcpu->arch.guest_fpu.state);
+       __kernel_fpu_begin(fpu);
+       __copy_kernel_to_fpregs(&fpu->state);
        trace_kvm_fpu(1);
 }
 
-- 
2.7.4