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

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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>
This commit is contained in:
Paolo Bonzini
2019-07-22 13:31:27 +02:00
parent cf64527bb3
commit ec269475cb
2 changed files with 6 additions and 5 deletions
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7
arch/x86/include/asm/kvm_host.h
View File

@ -607,15 +607,16 @@ struct kvm_vcpu_arch {
/* /*
* QEMU userspace and the guest each have their own FPU state. * QEMU userspace and the guest each have their own FPU state.
* In vcpu_run, we switch between the user, maintained in the * In vcpu_run, we switch between the user and guest FPU contexts.
* task_struct struct, and guest FPU contexts. While running a VCPU, * While running a VCPU, the VCPU thread will have the guest FPU
* the VCPU thread will have the guest FPU context. * context.
* *
* Note that while the PKRU state lives inside the fpu registers, * Note that while the PKRU state lives inside the fpu registers,
* it is switched out separately at VMENTER and VMEXIT time. The * it is switched out separately at VMENTER and VMEXIT time. The
* "guest_fpu" state here contains the guest FPU context, with the * "guest_fpu" state here contains the guest FPU context, with the
* host PRKU bits. * host PRKU bits.
*/ */
struct fpu user_fpu;
struct fpu *guest_fpu; struct fpu *guest_fpu;
u64 xcr0; u64 xcr0;

4
arch/x86/kvm/x86.c
View File

@ -8270,7 +8270,7 @@ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
{ {
fpregs_lock(); 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. */ /* PKRU is separately restored in kvm_x86_ops->run. */
__copy_kernel_to_fpregs(&vcpu->arch.guest_fpu->state, __copy_kernel_to_fpregs(&vcpu->arch.guest_fpu->state,
~XFEATURE_MASK_PKRU); ~XFEATURE_MASK_PKRU);
@ -8287,7 +8287,7 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
fpregs_lock(); fpregs_lock();
copy_fpregs_to_fpstate(vcpu->arch.guest_fpu); 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_mark_activate();
fpregs_unlock(); fpregs_unlock();