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

[Juergen Gross]

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@xxxxxxxx>
> > ---
> >   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?


Juergen
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