linux-kernel - Re: [PATCH 1/2] xen: prepare p2m list for memory hotplug

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Message-ID: <550B00E2.1060103@suse.com>
Date:	Thu, 19 Mar 2015 18:01:22 +0100
From:	Juergen Gross <jgross@...e.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	konrad.wilk@...cle.com, david.vrabel@...rix.com,
	daniel.kiper@...cle.com
Subject: Re: [PATCH 1/2] xen: prepare p2m list for memory hotplug

On 03/19/2015 04:53 PM, Boris Ostrovsky wrote:
> On 03/19/2015 10:31 AM, Juergen Gross wrote:
>> Commit 054954eb051f35e74b75a566a96fe756015352c8 ("xen: switch to linear
>> virtual mapped sparse p2m list") introduced a regression regarding to
>> memory hotplug for a pv-domain: as the virtual space for the p2m list
>> is allocated for the to be expected memory size of the domain only,
>> hotplugged memory above that size will not be usable by the domain.
>>
>> Correct this by using a configurable size for the p2m list in case of
>> memory hotplug enabled (default supported memory size is 512 GB for
>> 64 bit domains and 4 GB for 32 bit domains).
>>
>> Signed-off-by: Juergen Gross <jgross@...e.com>
>> ---
>>   arch/x86/xen/p2m.c  | 13 ++++++++++++-
>>   drivers/xen/Kconfig | 13 +++++++++++++
>>   2 files changed, 25 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
>> index 9f93af5..30e84ae 100644
>> --- a/arch/x86/xen/p2m.c
>> +++ b/arch/x86/xen/p2m.c
>> @@ -91,6 +91,17 @@ EXPORT_SYMBOL_GPL(xen_p2m_size);
>>   unsigned long xen_max_p2m_pfn __read_mostly;
>>   EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
>> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
>> +#ifdef CONFIG_X86_32
>> +BUILD_BUG_ON_MSG(CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT > 64)
>
> Will this work in Kconfig instead?
>
>      range 0 64 if CONFIG_X86_32

I'll give it a try.

Juergen

>
> -boris
>
>> +#endif
>> +#define P2M_LIMIT max(xen_max_p2m_pfn,                    \
>> +    ((unsigned long)((u64)CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT *    \
>> +    1024 * 1024 * 1024 / PAGE_SIZE)))
>> +#else
>> +#define P2M_LIMIT xen_max_p2m_pfn
>> +#endif
>> +
>>   static DEFINE_SPINLOCK(p2m_update_lock);
>>   static unsigned long *p2m_mid_missing_mfn;
>> @@ -387,7 +398,7 @@ void __init xen_vmalloc_p2m_tree(void)
>>       static struct vm_struct vm;
>>       vm.flags = VM_ALLOC;
>> -    vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn,
>> +    vm.size = ALIGN(sizeof(unsigned long) * P2M_LIMIT,
>>               PMD_SIZE * PMDS_PER_MID_PAGE);
>>       vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
>>       pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr,
>> vm.size);
>> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
>> index b812462..0a61ddf 100644
>> --- a/drivers/xen/Kconfig
>> +++ b/drivers/xen/Kconfig
>> @@ -55,6 +55,19 @@ config XEN_BALLOON_MEMORY_HOTPLUG
>>         In that case step 3 should be omitted.
>> +config XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
>> +    int
>> +    default 512 if X86_64
>> +    default 4 if X86_32
>> +    depends on XEN_HAVE_PVMMU
>> +    depends on XEN_BALLOON_MEMORY_HOTPLUG
>> +    help
>> +      Upper limit in GBs a pv domain can be expanded to using memory
>> +      hotplug.
>> +
>> +      This value is used to allocate enough space in internal tables
>> needed
>> +      for physical memory administration.
>> +
>>   config XEN_SCRUB_PAGES
>>       bool "Scrub pages before returning them to system"
>>       depends on XEN_BALLOON
>
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