linux-kernel - Re: [PATCH 0/7] KVM: Alleviate mmu_lock hold time when we start dirty logging

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Message-Id: <20130108194044.aa857582.yoshikawa_takuya_b1@lab.ntt.co.jp>
Date:	Tue, 8 Jan 2013 19:40:44 +0900
From:	Takuya Yoshikawa <yoshikawa_takuya_b1@....ntt.co.jp>
To:	Marcelo Tosatti <mtosatti@...hat.com>
Cc:	gleb@...hat.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/7] KVM: Alleviate mmu_lock hold time when we start
 dirty logging

On Mon, 7 Jan 2013 18:36:42 -0200
Marcelo Tosatti <mtosatti@...hat.com> wrote:

> Looks good, except patch 1 - 
> 
> a) don't understand why it is necessary and 

What's really necessary is to make sure that we don't call the function
for a deleted slot.  My explanation was wrong.

> b) not confident its safe - isnt clearing necessary for KVM_SET_MEMORY
> instances other than
> 
> !(old.flags & LOG_DIRTY) && (new.flags & LOG_DIRTY)

I think flushing shadows should be enough for other cases, e.g. moving a slot.

But I've changed the condition (see v2) to make it easier to understand:
  npages && LOG_DIRTY

Since remove_write_access() is for dirty logging, this condition should be safe.

Thanks,
	Takuya
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