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Date: Tue, 23 Jul 2019 08:42:27 +0800 From: Wanpeng Li <kernellwp@...il.com> To: Paolo Bonzini <pbonzini@...hat.com> Cc: LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>, "# v3 . 10+" <stable@...r.kernel.org> Subject: Re: [PATCH] Revert "kvm: x86: Use task structs fpu field for user" On Mon, 22 Jul 2019 at 20:49, Paolo Bonzini <pbonzini@...hat.com> wrote: > > 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@...r.kernel.org > Signed-off-by: Paolo Bonzini <pbonzini@...hat.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(¤t->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(¤t->thread.fpu.state); > + copy_kernel_to_fpregs(&vcpu->arch.user_fpu.state); > > fpregs_mark_activate(); > fpregs_unlock(); Looks good to me. Regards, Wanpeng Li
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