linux-kernel - Re: [PATCH v2 14/20] xen/grant-table: Make it running on 64KB granularity

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Date:	Thu, 16 Jul 2015 16:47:09 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Julien Grall <julien.grall@...rix.com>
CC:	<xen-devel@...ts.xenproject.org>,
	<linux-arm-kernel@...ts.infradead.org>, <ian.campbell@...rix.com>,
	<stefano.stabellini@...citrix.com>, <linux-kernel@...r.kernel.org>,
	David Vrabel <david.vrabel@...rix.com>,
	Russell King <linux@....linux.org.uk>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [PATCH v2 14/20] xen/grant-table: Make it running on 64KB
 granularity

On Thu, 9 Jul 2015, Julien Grall wrote:
> The Xen interface is using 4KB page granularity. This means that each
> grant is 4KB.
> 
> The current implementation allocates a Linux page per grant. On Linux
> using 64KB page granularity, only the first 4KB of the page will be
> used.
> 
> We could decrease the memory wasted by sharing the page with multiple
> grant. It will require some care with the {Set,Clear}ForeignPage macro.
> 
> Note that no changes has been made in the x86 code because both Linux
> and Xen will only use 4KB page granularity.
> 
> Signed-off-by: Julien Grall <julien.grall@...rix.com>
> Reviewed-by: David Vrabel <david.vrabel@...rix.com>
> Cc: Stefano Stabellini <stefano.stabellini@...citrix.com>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> ---
>     Changes in v2
>         - Add David's reviewed-by
> ---
>  arch/arm/xen/p2m.c        | 6 +++---
>  drivers/xen/grant-table.c | 6 +++---
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c
> index 887596c..0ed01f2 100644
> --- a/arch/arm/xen/p2m.c
> +++ b/arch/arm/xen/p2m.c
> @@ -93,8 +93,8 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
>  	for (i = 0; i < count; i++) {
>  		if (map_ops[i].status)
>  			continue;
> -		set_phys_to_machine(map_ops[i].host_addr >> PAGE_SHIFT,
> -				    map_ops[i].dev_bus_addr >> PAGE_SHIFT);
> +		set_phys_to_machine(map_ops[i].host_addr >> XEN_PAGE_SHIFT,
> +				    map_ops[i].dev_bus_addr >> XEN_PAGE_SHIFT);
>  	}
>  
>  	return 0;
> @@ -108,7 +108,7 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
>  	int i;
>  
>  	for (i = 0; i < count; i++) {
> -		set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,
> +		set_phys_to_machine(unmap_ops[i].host_addr >> XEN_PAGE_SHIFT,
>  				    INVALID_P2M_ENTRY);
>  	}
>  
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index 3679293..0a1f903 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c

The arm part is fine, but aren't you missing the change to RPP and SPP?


> @@ -668,7 +668,7 @@ int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
>  	if (xen_auto_xlat_grant_frames.count)
>  		return -EINVAL;
>  
> -	vaddr = xen_remap(addr, PAGE_SIZE * max_nr_gframes);
> +	vaddr = xen_remap(addr, XEN_PAGE_SIZE * max_nr_gframes);
>  	if (vaddr == NULL) {
>  		pr_warn("Failed to ioremap gnttab share frames (addr=%pa)!\n",
>  			&addr);
> @@ -680,7 +680,7 @@ int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
>  		return -ENOMEM;
>  	}
>  	for (i = 0; i < max_nr_gframes; i++)
> -		pfn[i] = PFN_DOWN(addr) + i;
> +		pfn[i] = XEN_PFN_DOWN(addr) + i;
>  
>  	xen_auto_xlat_grant_frames.vaddr = vaddr;
>  	xen_auto_xlat_grant_frames.pfn = pfn;
> @@ -1004,7 +1004,7 @@ static void gnttab_request_version(void)
>  {
>  	/* Only version 1 is used, which will always be available. */
>  	grant_table_version = 1;
> -	grefs_per_grant_frame = PAGE_SIZE / sizeof(struct grant_entry_v1);
> +	grefs_per_grant_frame = XEN_PAGE_SIZE / sizeof(struct grant_entry_v1);
>  	gnttab_interface = &gnttab_v1_ops;
>  
>  	pr_info("Grant tables using version %d layout\n", grant_table_version);
> -- 
> 2.1.4
> 
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