linux-kernel - Re: [Xen-devel] [Patch V2 1/2] xen: prepare p2m list for memory hotplug

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Message-ID: <551029D3.7090306@citrix.com>
Date:	Mon, 23 Mar 2015 14:57:23 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Juergen Gross <jgross@...e.com>,
	David Vrabel <david.vrabel@...rix.com>,
	<linux-kernel@...r.kernel.org>, <xen-devel@...ts.xensource.com>,
	<konrad.wilk@...cle.com>, <boris.ostrovsky@...cle.com>,
	<daniel.kiper@...cle.com>, <pebolle@...cali.nl>
Subject: Re: [Xen-devel] [Patch V2 1/2] xen: prepare p2m list for memory hotplug

On 23/03/15 14:29, Juergen Gross wrote:
> On 03/23/2015 01:46 PM, David Vrabel wrote:
>> On 20/03/15 12:55, 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  | 10 +++++++++-
>>>   drivers/xen/Kconfig | 14 ++++++++++++++
>>>   2 files changed, 23 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
>>> index 9f93af5..b47124d 100644
>>> --- a/arch/x86/xen/p2m.c
>>> +++ b/arch/x86/xen/p2m.c
>>> @@ -91,6 +91,12 @@ 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
>>> +#define P2M_LIMIT CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
>>> +#else
>>> +#define P2M_LIMIT 0
>>> +#endif
>>> +
>>>   static DEFINE_SPINLOCK(p2m_update_lock);
>>>
>>>   static unsigned long *p2m_mid_missing_mfn;
>>> @@ -385,9 +391,11 @@ static void __init xen_rebuild_p2m_list(unsigned
>>> long *p2m)
>>>   void __init xen_vmalloc_p2m_tree(void)
>>>   {
>>>       static struct vm_struct vm;
>>> +    unsigned long p2m_limit;
>>>
>>> +    p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 /
>>> PAGE_SIZE;
>>>       vm.flags = VM_ALLOC;
>>> -    vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn,
>>> +    vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn,
>>> 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..0f1b509 100644
>>> --- a/drivers/xen/Kconfig
>>> +++ b/drivers/xen/Kconfig
>>> @@ -55,6 +55,20 @@ config XEN_BALLOON_MEMORY_HOTPLUG
>>>
>>>         In that case step 3 should be omitted.
>>>
>>> +config XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
>>> +    int
>>
>> Because you've not supplied a summary for this option, it is not user
>> configurable.  Is this intentional?
> 
> No. Sorry, I just tested it via editing .config, not using the menues.
> Can you add it when committing (e.g. "Upper limit in GBs a pv domain
> can be expanded to using memory hotplug")?
> 
> Or should I send another patch?

I'll fix it up.

David
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