Re: [Xen-devel] [PATCH 2/2] xen: before ballooning hotplugged memory, set frames to invalid

[Juergen Gross]

On 03/19/2015 05:18 PM, David Vrabel wrote:
> On 19/03/15 14:31, Juergen Gross wrote:
> > Commit 25b884a83d487fd62c3de7ac1ab5549979188482 ("x86/xen: set
> > regions above the end of RAM as 1:1") introduced a regression.
> >
> > To be able to add memory pages which were added via memory hotplug to
> > a pv domain, the pages must be "invalid" instead of "identity" in the
> > p2m list before they can be added.
> [...]
> > --- a/drivers/xen/balloon.c
> > +++ b/drivers/xen/balloon.c
> > @@ -221,15 +221,24 @@ static bool balloon_is_inflated(void)
> >
> >   static enum bp_state reserve_additional_memory(long credit)
> >   {
> > -	int nid, rc;
> > +	int nid, rc = 0;
> >   	u64 hotplug_start_paddr;
> >   	unsigned long balloon_hotplug = credit;
> > +	unsigned long pfn;
> >
> >   	hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
> >   	balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
> >   	nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
> >
> > -	rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
> > +	for (pfn = PFN_DOWN(hotplug_start_paddr);
> > +	     !rc && pfn < PFN_DOWN(hotplug_start_paddr) + balloon_hotplug;
> > +	     pfn++)
> > +		if (!set_phys_to_machine(pfn, INVALID_P2M_ENTRY))
> > +			rc = 1;
>
>      rc = -ENOMEM;

I used the value 1 on purpose to be able to identify the case by the
value printed in the warning below.

>      break;

Why? !rc is already tested in the for() clause.

> > +
> > +	if (!rc)
> > +		rc = add_memory(nid, hotplug_start_paddr,
> > +				balloon_hotplug << PAGE_SHIFT);
>
> Use else here.

Huh? I want the message to be printed if either set_phys_to_machine()
or add_memory() failed.

> >   	if (rc) {
> >   		pr_warn("Cannot add additional memory (%i)\n", rc);


Juergen

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