[PATCH] KVM: Initialize fpu state in preemptible context

[Avi Kivity]

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.

Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
---
 arch/x86/kernel/i387.c |    1 +
 arch/x86/kvm/x86.c     |    3 +++
 2 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 58bb239..e60c38c 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 8652643..fd93cda 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5351,6 +5351,9 @@ 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);
 
-- 
1.7.1


--------------020201020807000707070104--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/