FAILED: patch "[PATCH] kvm: x86: fix WARN due to uninitialized guest FPU state" failed to apply to 4.14-stable tree

From 5663d8f9bbe4bf15488f7351efb61ea20fa6de06 Mon Sep 17 00:00:00 2001

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5663d8f9bbe4bf15488f7351efb61ea20fa6de06 Mon Sep 17 00:00:00 2001
From: Peter Xu <[email protected]>
Date: Tue, 12 Dec 2017 17:15:02 +0100
Subject: [PATCH] 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 [email protected]

Fixes f775b13eedee2f7f3c6fdd4e90fb79090ce5d339

Signed-off-by Peter Xu <[email protected]>

Signed-off-by Paolo Bonzini <[email protected]>

arch/x86/kvm/x86.c +4 -8

index 154ea27746e9..56d036b9ad75 100644
@@ -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)
 {
-	struct fpu *fpu = &current->thread.fpu;
 	int r;
 
-	fpu__initialize(fpu);
-
 	kvm_sigset_activate(vcpu);
 
+	kvm_load_guest_fpu(vcpu);
+
 	if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
 		if (kvm_run->immediate_exit) {
 			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)) {
 		int (*cui)(struct kvm_vcpu *) = vcpu->arch.complete_userspace_io;
 		vcpu->arch.complete_userspace_io = NULL;
 		r = cui(vcpu);
 		if (r <= 0)
-			goto out_fpu;
+			goto out;
 	} else
 		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
 		r = vcpu_run(vcpu);
 
-out_fpu:
-	kvm_put_guest_fpu(vcpu);
 out:
+	kvm_put_guest_fpu(vcpu);
 	post_kvm_run_save(vcpu);
 	kvm_sigset_deactivate(vcpu);