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

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Date:	Thu, 3 Sep 2015 14:26:32 +0200
From:	Juergen Gross <jgross@...e.com>
To:	Roger Pau Monné <roger.pau@...rix.com>,
	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>,
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH] xen/p2m: fix extra memory regions accounting

On 09/03/2015 02:15 PM, Roger Pau Monné wrote:
> 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);

No, PAGE_ALIGN() already does that.


Juergen

>
> 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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