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kvm: x86: fix WARN due to uninitialized guest FPU state 

------------[ 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

where kvm_put_guest_fpu is called without a prior kvm_load_guest_fpu.
To fix it, move kvm_load_guest_fpu to the very beginning of
kvm_arch_vcpu_ioctl_run.

Cc: stable@vger.kernel.org
Fixes: f775b13eed
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Peter Xu 2017-12-12 17:15:02 +01:00 committed by Paolo Bonzini
parent d73235d17b
commit 5663d8f9bb
1 changed files with 4 additions and 8 deletions
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12
arch/x86/kvm/x86.c
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@ -7264,13 +7264,12 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{ {
struct fpu *fpu = &current->thread.fpu;
int r; int r;
fpu__initialize(fpu);
kvm_sigset_activate(vcpu); kvm_sigset_activate(vcpu);
kvm_load_guest_fpu(vcpu);
if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) { if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
if (kvm_run->immediate_exit) { if (kvm_run->immediate_exit) {
r = -EINTR; r = -EINTR;
@ -7296,14 +7295,12 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
} }
} }
kvm_load_guest_fpu(vcpu);
if (unlikely(vcpu->arch.complete_userspace_io)) { if (unlikely(vcpu->arch.complete_userspace_io)) {
int (*cui)(struct kvm_vcpu *) = vcpu->arch.complete_userspace_io; int (*cui)(struct kvm_vcpu *) = vcpu->arch.complete_userspace_io;
vcpu->arch.complete_userspace_io = NULL; vcpu->arch.complete_userspace_io = NULL;
r = cui(vcpu); r = cui(vcpu);
if (r <= 0) if (r <= 0)
goto out_fpu; goto out;
} else } else
WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed); WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
@ -7312,9 +7309,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
else else
r = vcpu_run(vcpu); r = vcpu_run(vcpu);
out_fpu:
kvm_put_guest_fpu(vcpu);
out: out:
kvm_put_guest_fpu(vcpu);
post_kvm_run_save(vcpu); post_kvm_run_save(vcpu);
kvm_sigset_deactivate(vcpu); kvm_sigset_deactivate(vcpu);