linux-kernel - Re: [PATCH 07/10] KVM: introduce readonly_fault

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Message-ID: <5008C8DE.4000602@linux.vnet.ibm.com>
Date:	Fri, 20 Jul 2012 10:56:30 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 07/10] KVM: introduce readonly_fault_pfn

On 07/19/2012 06:15 PM, Avi Kivity wrote:
> On 07/17/2012 05:44 PM, Xiao Guangrong wrote:
>> Introduce readonly_fault_pfn, in the later patch, it indicates failure
>> when we try to get a writable pfn from the readonly memslot
>>
>> +
>>  inline int kvm_is_mmio_pfn(pfn_t pfn)
>>  {
>>  	if (pfn_valid(pfn)) {
>> @@ -949,13 +952,15 @@ EXPORT_SYMBOL_GPL(kvm_disable_largepages);
>>
>>  int is_error_page(struct page *page)
>>  {
>> -	return page == bad_page || page == hwpoison_page || page == fault_page;
>> +	return page == bad_page || page == hwpoison_page || page == fault_page
>> +		|| page == readonly_fault_page;
> 
> All those checks are slow, and get_page(fault_page) etc. isn't very
> scalable.
> 
> We should move to ERR_PTR() etc.  We could use ENOENT, EHWPOISON,
> EFAULT, and EROFS for the above, or maybe there are better matches.
> 

Good point. I will do it in the next version, thank you, Avi!

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