linux-kernel - Re: [PATCH] xen/p2m: fix extra memory regions accounting

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Date:	Thu, 3 Sep 2015 14:15:11 +0200
From:	Roger Pau Monné <roger.pau@...rix.com>
To:	<linux-kernel@...r.kernel.org>
CC:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>,
	"Juergen Gross" <jgross@...e.com>, <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH] xen/p2m: fix extra memory regions accounting

El 03/09/15 a les 14.05, Roger Pau Monne ha escrit:
> On systems with memory maps with ranges that don't end at page boundaries,
> like:
> 
> [...]
> (XEN)  0000000000100000 - 00000000dfdf9c00 (usable)
> (XEN)  00000000dfdf9c00 - 00000000dfe4bc00 (ACPI NVS)
> [...]
> 
> xen_add_extra_mem will create a protected range that ends up at 0xdfdf9c00,
> but the function used to check if a memory address is inside of a protected
> range works with pfns, which means that an attempt to map 0xdfdf9c00 will be
> refused because the check is performed against 0xdfdf9000 instead of
> 0xdfdf9c00.
> 
> In order to fix this, make sure that the ranges that are added to the
> xen_extra_mem array are aligned to page boundaries.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@...rix.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: David Vrabel <david.vrabel@...rix.com>
> Cc: Juergen Gross <jgross@...e.com>
> Cc: xen-devel@...ts.xenproject.org
> ---
> AFAICT this patch needs to be backported to 3.19, 4.0, 4.1 and 4.2.
> ---
>  arch/x86/xen/setup.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index 55f388e..dcf5865 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -68,6 +68,9 @@ static void __init xen_add_extra_mem(phys_addr_t start, phys_addr_t size)
>  {
>  	int i;
>  
> +	start = PAGE_ALIGN(start);

Sorry, I didn't remember to update the patch before sending it, but I
think this should instead be:

start = round_up(start, PAGE_SIZE);

Here and below.

> +	size &= PAGE_MASK;
> +
>  	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
>  		/* Add new region. */
>  		if (xen_extra_mem[i].size == 0) {
> @@ -92,6 +95,9 @@ static void __init xen_del_extra_mem(phys_addr_t start, phys_addr_t size)
>  	int i;
>  	phys_addr_t start_r, size_r;
>  
> +	start = PAGE_ALIGN(start);
> +	size &= PAGE_MASK;
> +
>  	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
>  		start_r = xen_extra_mem[i].start;
>  		size_r = xen_extra_mem[i].size;
> 

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