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Date: Wed, 12 May 2010 15:27:46 +0900
From: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
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To: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [RFC][PATCH RFC 10/12] KVM: move dirty bitmaps to user space
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Cc: linux-arch@vger.kernel.org, arnd@arndb.de, kvm@vger.kernel.org,
	kvm-ia64@vger.kernel.org, fernando@oss.ntt.co.jp, x86@kernel.org,
	agraf@suse.de, kvm-ppc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
	mingo@redhat.com, paulus@samba.org, avi@redhat.com,
	hpa@zytor.com, tglx@linutronix.de,
	Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
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>>   	r = 0;
>> @@ -1195,11 +1232,16 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
>>   	gfn = unalias_gfn(kvm, gfn);
>>   	memslot = gfn_to_memslot_unaliased(kvm, gfn);
>>   	if (memslot&&  memslot->dirty_bitmap) {
>> -		unsigned long rel_gfn = gfn - memslot->base_gfn;
>> +		int nr = generic_le_bit_offset(gfn - memslot->base_gfn);
>>
>> -		generic___set_le_bit(rel_gfn, memslot->dirty_bitmap);
>> +		if (kvm_set_bit_user(nr, memslot->dirty_bitmap))
>> +			goto out_fault;
>
> mark_page_dirty is called with the mmu_lock spinlock held in set_spte.
> Must find a way to move it outside of the spinlock section.
>

Oh, it's a serious problem. I have to consider it.


Thanks,
   Takuya