linux-kernel - Re: [PATCH v12 12/18] xen/grants: Remove gnttab_max_grant_frames dependency on gnttab

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Date:	Fri, 3 Jan 2014 16:40:26 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	<linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>,
	<boris.ostrovsky@...cle.com>, <david.vrabel@...rix.com>,
	<stefano.stabellini@...citrix.com>, <mukesh.rathor@...cle.com>
Subject: Re: [PATCH v12 12/18] xen/grants: Remove gnttab_max_grant_frames
 dependency on gnttab_init.

On Tue, 31 Dec 2013, Konrad Rzeszutek Wilk wrote:
> The function gnttab_max_grant_frames() returns the maximum amount
> of frames (pages) of grants we can have. Unfortunatly it was
> dependent on gnttab_init() having been run before to initialize
> the boot max value (boot_max_nr_grant_frames).
> 
> This meant that users of gnttab_max_grant_frames would always
> get a zero value if they called before gnttab_init() - such as
> 'platform_pci_init' (drivers/xen/platform-pci.c).
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

Acked-by: Stefano Stabellini <stefano.stabellini@...citrix.com>


>  drivers/xen/grant-table.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index aa846a4..99399cb 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -62,7 +62,6 @@
>  
>  static grant_ref_t **gnttab_list;
>  static unsigned int nr_grant_frames;
> -static unsigned int boot_max_nr_grant_frames;
>  static int gnttab_free_count;
>  static grant_ref_t gnttab_free_head;
>  static DEFINE_SPINLOCK(gnttab_list_lock);
> @@ -827,6 +826,11 @@ static unsigned int __max_nr_grant_frames(void)
>  unsigned int gnttab_max_grant_frames(void)
>  {
>  	unsigned int xen_max = __max_nr_grant_frames();
> +	static unsigned int boot_max_nr_grant_frames;
> +
> +	/* First time, initialize it properly. */
> +	if (!boot_max_nr_grant_frames)
> +		boot_max_nr_grant_frames = __max_nr_grant_frames();
>  
>  	if (xen_max > boot_max_nr_grant_frames)
>  		return boot_max_nr_grant_frames;
> @@ -1227,13 +1231,12 @@ int gnttab_init(void)
>  
>  	gnttab_request_version();
>  	nr_grant_frames = 1;
> -	boot_max_nr_grant_frames = __max_nr_grant_frames();
>  
>  	/* Determine the maximum number of frames required for the
>  	 * grant reference free list on the current hypervisor.
>  	 */
>  	BUG_ON(grefs_per_grant_frame == 0);
> -	max_nr_glist_frames = (boot_max_nr_grant_frames *
> +	max_nr_glist_frames = (gnttab_max_grant_frames() *
>  			       grefs_per_grant_frame / RPP);
>  
>  	gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
> -- 
> 1.8.3.1
> 
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