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

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Date:	Thu, 19 Jul 2012 13:15:04 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.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 07/17/2012 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.

>  }
>  EXPORT_SYMBOL_GPL(is_error_page);
> 
>  int is_error_pfn(pfn_t pfn)
>  {
> -	return pfn == bad_pfn || pfn == hwpoison_pfn || pfn == fault_pfn;
> +	return pfn == bad_pfn || pfn == hwpoison_pfn || pfn == fault_pfn
> +		|| pfn == readonly_fault_pfn;
>  }

And a similar change here.
-- 
error compiling committee.c: too many arguments to function


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