On 01/11/2011 11:49 AM, Avi Kivity wrote:
On 01/10/2011 09:31 PM, Kirill A. Shutemov wrote:
On Mon, Jan 10, 2011 at 10:52:05AM -0600, Christoph Lameter wrote:
>
> On Mon, 10 Jan 2011, Kirill A. Shutemov wrote:
>
> > Every time I run qemu with KVM enabled I get this in dmesg:
> >
> > [ 182.878328] BUG: sleeping function called from invalid
context at mm/slub.c:793
> > [ 182.878339] in_atomic(): 1, irqs_disabled(): 0, pid: 4992,
name: qemu
> > [ 182.878355] Pid: 4992, comm: qemu Not tainted 2.6.37+ #31
> > [ 182.878361] Call Trace:
> > [ 182.878381] [<c104e317>] ? __might_sleep+0xd0/0xd7
> > [ 182.878394] [<c10ec337>] ?
slab_pre_alloc_hook.clone.39+0x23/0x27
> > [ 182.878404] [<c10ece27>] ? kmem_cache_alloc+0x22/0xc8
> > [ 182.878414] [<c1030221>] ? init_fpu+0x44/0x7b
>
> fpu_alloc() does call kmem_cache_alloc with GFP_KERNEL although we
are in
> an atomic context.
Something like this?
---
From 7c6fbfed72e7d22cbdf7393f9711d521e0fbb4a6 Mon Sep 17 00:00:00 2001
From: Kirill A. Shutemov<kirill@xxxxxxxxxxxxx>
Date: Mon, 10 Jan 2011 21:24:23 +0200
Subject: [PATCH] x86, fpu_alloc(): call kmem_cache_alloc() with
GFP_ATOMIC
[ 182.878328] BUG: sleeping function called from invalid context at
mm/slub.c:793
[ 182.878339] in_atomic(): 1, irqs_disabled(): 0, pid: 4992, name: qemu
[ 182.878355] Pid: 4992, comm: qemu Not tainted 2.6.37+ #31
[ 182.878361] Call Trace:
[ 182.878381] [<c104e317>] ? __might_sleep+0xd0/0xd7
[ 182.878394] [<c10ec337>] ? slab_pre_alloc_hook.clone.39+0x23/0x27
[ 182.878404] [<c10ece27>] ? kmem_cache_alloc+0x22/0xc8
[ 182.878414] [<c1030221>] ? init_fpu+0x44/0x7b
[ 182.878426] [<c130cc29>] ? do_device_not_available+0x0/0x1b
[ 182.878435] [<c1030221>] ? init_fpu+0x44/0x7b
[ 182.878444] [<c102a588>] ? math_state_restore+0x24/0x47
[ 182.878453] [<c130cc39>] ? do_device_not_available+0x10/0x1b
[ 182.878462] [<c130c4ab>] ? error_code+0x67/0x6c
[ 182.878475] [<c1012340>] ? kvm_load_guest_fpu+0xa1/0xaa
[ 182.878484] [<c1013364>] ? kvm_arch_vcpu_ioctl_run+0x798/0xbe8
[ 182.878496] [<c1004523>] ? kvm_vcpu_ioctl+0x105/0x46e
[ 182.878508] [<c107dce0>] ? get_futex_key+0x73/0x132
[ 182.878517] [<c107e352>] ? futex_wake+0xb6/0xc0
[ 182.878527] [<c107f8d6>] ? do_futex+0x87/0x669
[ 182.878535] [<c100441e>] ? kvm_vcpu_ioctl+0x0/0x46e
[ 182.878545] [<c1101ebf>] ? do_vfs_ioctl+0x4a0/0x4d1
[ 182.878554] [<c130e348>] ? do_page_fault+0x2eb/0x316
[ 182.878564] [<c1101f36>] ? sys_ioctl+0x46/0x68
[ 182.878572] [<c130bdc0>] ? syscall_call+0x7/0xb
[ 182.878585] [<c1300000>] ? aer_probe+0x1da/0x274
Signed-off-by: Kirill A. Shutemov<kirill@xxxxxxxxxxxxx>
---
arch/x86/include/asm/i387.h | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index ef32890..8b896dd 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -426,7 +426,7 @@ static inline int fpu_alloc(struct fpu *fpu)
{
if (fpu_allocated(fpu))
return 0;
- fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
+ fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_ATOMIC);
if (!fpu->state)
return -ENOMEM;
WARN_ON((unsigned long)fpu->state& 15);
If this fails, a task will be killed. I'll patch kvm to ensure that
the fpu is initialized.
Please try out the attached patch.
--
error compiling committee.c: too many arguments to function
>From f3a6041b5bb3bf7c88f9694a66d7f34be2f78845 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@xxxxxxxxxx>
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.
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
