linux-kernel - Re: [PATCH v2 4/5] KVM: MMU: introduce page_fault_start and page_fault

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Message-ID: <50582DA4.8060000@linux.vnet.ibm.com>
Date:	Tue, 18 Sep 2012 16:15:32 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Avi Kivity <avi@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 4/5] KVM: MMU: introduce page_fault_start and page_fault_end

On 09/15/2012 11:25 PM, Marcelo Tosatti wrote:
> On Fri, Sep 14, 2012 at 05:59:06PM +0800, Xiao Guangrong wrote:
>> Wrap the common operations into these two functions
>>
>> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
> 
> Why? I think people are used to 
> 
> spin_lock(lock)
> sequence
> spin_unlock(lock)

Marcelo,

There are many functions use this style that wrap the lock into the
_start and _end functions in kernel (eg.: cgroup_pidlist_start and
cgroup_pidlist_stop in kernel/cgroup.c).

Actually, i just wanted to remove below duplicate ugly code:

	if (!is_error_pfn(pfn))
		kvm_release_pfn_clean(pfn);

> 
> So its easy to verify whether access to data structures are protected.
> 
> Unrelated to this patch, one opportunity i see to simplify this
> code is:
> 
> - error pfn / mmio pfn / invalid pfn relation
> 
> Have the meaning of this bits unified in a single function/helper, see
> comment to patch 1 (perhaps you can further improve).

Sorry, more detail?

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