linux-kernel - Re: [PATCHv2 09/10] x86/xen: export xen_alloc_p2m

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Date:	Fri, 24 Jul 2015 14:51:36 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	David Vrabel <david.vrabel@...rix.com>
Cc:	xen-devel@...ts.xenproject.org,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Daniel Kiper <daniel.kiper@...cle.com>
Subject: Re: [PATCHv2 09/10] x86/xen: export xen_alloc_p2m_entry()

On Fri, Jul 24, 2015 at 12:47:47PM +0100, David Vrabel wrote:
> Rename alloc_p2m() to xen_alloc_p2m_entry() and export it.
> 
> This is useful for ensuring that a p2m entry is allocated (i.e., not a
> shared missing or identity entry) so that subsequent set_phys_to_machine()
> calls will require no further allocations.
> 
> Signed-off-by: David Vrabel <david.vrabel@...rix.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  arch/x86/include/asm/xen/page.h |  2 ++
>  arch/x86/xen/p2m.c              | 16 ++++++++++------
>  2 files changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
> index c44a5d5..960b380 100644
> --- a/arch/x86/include/asm/xen/page.h
> +++ b/arch/x86/include/asm/xen/page.h
> @@ -45,6 +45,8 @@ extern unsigned long *xen_p2m_addr;
>  extern unsigned long  xen_p2m_size;
>  extern unsigned long  xen_max_p2m_pfn;
>  
> +extern int xen_alloc_p2m_entry(unsigned long pfn);
> +
>  extern unsigned long get_phys_to_machine(unsigned long pfn);
>  extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);
>  extern bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> index 8b7f18e..ef93ccf 100644
> --- a/arch/x86/xen/p2m.c
> +++ b/arch/x86/xen/p2m.c
> @@ -503,7 +503,7 @@ static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
>   * the new pages are installed with cmpxchg; if we lose the race then
>   * simply free the page we allocated and use the one that's there.
>   */
> -static bool alloc_p2m(unsigned long pfn)
> +int xen_alloc_p2m_entry(unsigned long pfn)
>  {
>  	unsigned topidx, mididx;
>  	unsigned long *top_mfn_p, *mid_mfn;
> @@ -524,7 +524,7 @@ static bool alloc_p2m(unsigned long pfn)
>  		/* PMD level is missing, allocate a new one */
>  		ptep = alloc_p2m_pmd(addr, pte_pg);
>  		if (!ptep)
> -			return false;
> +			return -ENOMEM;
>  	}
>  
>  	if (p2m_top_mfn) {
> @@ -541,7 +541,7 @@ static bool alloc_p2m(unsigned long pfn)
>  
>  			mid_mfn = alloc_p2m_page();
>  			if (!mid_mfn)
> -				return false;
> +				return -ENOMEM;
>  
>  			p2m_mid_mfn_init(mid_mfn, p2m_missing);
>  
> @@ -567,7 +567,7 @@ static bool alloc_p2m(unsigned long pfn)
>  
>  		p2m = alloc_p2m_page();
>  		if (!p2m)
> -			return false;
> +			return -ENOMEM;
>  
>  		if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
>  			p2m_init(p2m);
> @@ -590,8 +590,9 @@ static bool alloc_p2m(unsigned long pfn)
>  			free_p2m_page(p2m);
>  	}
>  
> -	return true;
> +	return 0;
>  }
> +EXPORT_SYMBOL(xen_alloc_p2m);
>  
>  unsigned long __init set_phys_range_identity(unsigned long pfn_s,
>  				      unsigned long pfn_e)
> @@ -648,7 +649,10 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
>  bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
>  {
>  	if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
> -		if (!alloc_p2m(pfn))
> +		int ret;
> +
> +		ret = xen_alloc_p2m_entry(pfn);
> +		if (ret < 0)
>  			return false;
>  
>  		return __set_phys_to_machine(pfn, mfn);
> -- 
> 2.1.4
> 
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