linux-kernel - Re: [patch] kvm: fix GFP_KERNEL allocation in atomic section in kvm_dev_ioctl_create

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Date:	Thu, 28 Dec 2006 13:55:44 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Avi Kivity <avi@...ranet.com>
Cc:	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>,
	Linus Torvalds <torvalds@...l.org>
Subject: Re: [patch] kvm: fix GFP_KERNEL allocation in atomic section in kvm_dev_ioctl_create_vcpu()


* Avi Kivity <avi@...ranet.com> wrote:

> >fix a GFP_KERNEL allocation in atomic section bug: 
> >kvm_dev_ioctl_create_vcpu() called kvm_mmu_init(), which calls 
> >alloc_pages(), while holding the vcpu. The fix is to set up the MMU 
> >state earlier, it does not require a loaded CPU state.
> 
> Yes it does.  It calls nonpaging_init_context() which calls 
> vmx_set_cr3() which promptly trashes address space of the VM that 
> previously ran on that vcpu (or, if there were none, logs a vmwrite 
> error).

ok, i missed that. Nevertheless the problem of the nonatomic alloc 
remains. I guess a kvm_mmu_init() needs to be split into 
kvm_mmu_create() and kvm_mmu_setup()?

	Ingo
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