From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
------------[ 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@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run)
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
---
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(&fpu->state);
+ fpu->initialized = 1;
+ }
kvm_sigset_activate(vcpu);
--
2.7.4