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

[Juergen Gross]

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@xxxxxxxx>
> > ---
> >   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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