[PATCH] Revert "kvm: x86: Use task structs fpu field for user"

Paolo Bonzini
2019-07-22T11:56:43Z

This reverts commit 240c35a3783ab9b3a0afaba0dde7291295680a6b
("kvm: x86: Use task structs fpu field for user", 2018-11-06).
The commit is broken and causes QEMU's FPU state to be destroyed
when KVM_RUN is preempted.

Fixes: 240c35a3783a ("kvm: x86: Use task structs fpu field for user")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 7 ++++---
arch/x86/kvm/x86.c | 4 ++--
2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0cc5b611a113..b2f1ffb937af 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -607,15 +607,16 @@ struct kvm_vcpu_arch {

/*
* QEMU userspace and the guest each have their own FPU state.
- * In vcpu_run, we switch between the user, maintained in the
- * task_struct struct, and guest FPU contexts. While running a VCPU,
- * the VCPU thread will have the guest FPU context.
+ * In vcpu_run, we switch between the user and guest FPU contexts.
+ * While running a VCPU, the VCPU thread will have the guest FPU
+ * context.
*
* Note that while the PKRU state lives inside the fpu registers,
* it is switched out separately at VMENTER and VMEXIT time. The
* "guest_fpu" state here contains the guest FPU context, with the
* host PRKU bits.
*/
+ struct fpu user_fpu;
struct fpu *guest_fpu;

u64 xcr0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 58305cf81182..cf2afdf8facf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8270,7 +8270,7 @@ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
{
fpregs_lock();

- copy_fpregs_to_fpstate(&current->thread.fpu);
+ copy_fpregs_to_fpstate(&vcpu->arch.user_fpu);
/* PKRU is separately restored in kvm_x86_ops->run. */
__copy_kernel_to_fpregs(&vcpu->arch.guest_fpu->state,
~XFEATURE_MASK_PKRU);
@@ -8287,7 +8287,7 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
fpregs_lock();

copy_fpregs_to_fpstate(vcpu->arch.guest_fpu);
- copy_kernel_to_fpregs(&current->thread.fpu.state);
+ copy_kernel_to_fpregs(&vcpu->arch.user_fpu.state);

fpregs_mark_activate();
fpregs_unlock();
--
1.8.3.1