From e5c301428294cb8925667c9ee39f817c4ab1c2c9 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@redhat.com>
Date: Tue, 11 Jan 2011 12:15:54 +0200
Subject: [PATCH] KVM: Initialize fpu state in preemptible context

init_fpu() (which is indirectly called by the fpu switching code) assumes
it is in process context.  Rather than makeing init_fpu() use an atomic
allocation, which can cause a task to be killed, make sure the fpu is
already initialized when we enter the run loop.

KVM-Stable-Tag.
Reported-and-tested-by: Kirill A. Shutemov <kas@openvz.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
 arch/x86/kernel/i387.c | 1 +
 arch/x86/kvm/x86.c     | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 58bb239a2fd76..e60c38cc0eed5 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -169,6 +169,7 @@ int init_fpu(struct task_struct *tsk)
 	set_stopped_child_used_math(tsk);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(init_fpu);
 
 /*
  * The xstateregs_active() routine is the same as the fpregs_active() routine,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fa708c9a74377..9dda70dffac19 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5376,6 +5376,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	int r;
 	sigset_t sigsaved;
 
+	if (!tsk_used_math(current) && init_fpu(current))
+		return -ENOMEM;
+
 	if (vcpu->sigset_active)
 		sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved);
 
-- 
GitLab