linux-kernel - Re: [RFC][PATCH RFC 10/12] KVM: move dirty bitmaps to user space

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Message-ID: <4BEA4A62.20100@oss.ntt.co.jp>
Date:	Wed, 12 May 2010 15:27:46 +0900
From:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Takuya Yoshikawa <takuya.yoshikawa@...il.com>, avi@...hat.com,
	agraf@...e.de, fernando@....ntt.co.jp, kvm@...r.kernel.org,
	kvm-ppc@...r.kernel.org, kvm-ia64@...r.kernel.org,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, benh@...nel.crashing.org, paulus@...ba.org,
	linuxppc-dev@...abs.org, arnd@...db.de, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH RFC 10/12] KVM: move dirty bitmaps to user space


>>   	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
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