From: Wanpeng Li wanpeng.li@hotmail.com
------------[ cut here ]------------ Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers. WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90 CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10 RIP: 0010:ex_handler_fprestore+0x88/0x90 Call Trace: fixup_exception+0x4e/0x60 do_general_protection+0xff/0x270 general_protection+0x22/0x30 RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm] RSP: 0018:ffff8803d5627810 EFLAGS: 00010246 kvm_vcpu_reset+0x3b4/0x3c0 [kvm] kvm_apic_accept_events+0x1c0/0x240 [kvm] kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm] kvm_vcpu_ioctl+0x479/0x880 [kvm] do_vfs_ioctl+0x142/0x9a0 SyS_ioctl+0x74/0x80 do_syscall_64+0x15f/0x600
This can be reproduced by running any testcase in kvm-unit-tests since the qemu userspace FPU context is not initialized, which results in the init path from kvm_apic_accept_events() will load/put qemu userspace FPU context w/o initialized. In addition, w/o this splatting we still should initialize vcpu->arch.user_fpu instead of current->thread.fpu. This patch fixes it by initializing qemu user FPU context if it is uninitialized before KVM_RUN.
Cc: Paolo Bonzini pbonzini@redhat.com Cc: Radim Krčmář rkrcmar@redhat.com Cc: Rik van Riel riel@redhat.com Cc: stable@vger.kernel.org Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run) Signed-off-by: Wanpeng Li wanpeng.li@hotmail.com --- arch/x86/kvm/x86.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a92b22f..063a643 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) { - struct fpu *fpu = ¤t->thread.fpu; + struct fpu *fpu = &vcpu->arch.user_fpu; int r;
- fpu__initialize(fpu); + if (!fpu->initialized) { + fpstate_init(&vcpu->arch.user_fpu.state); + fpu->initialized = 1; + }
kvm_sigset_activate(vcpu);