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

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Message-ID: <550AF6EE.9010404@citrix.com>
Date:	Thu, 19 Mar 2015 16:18:54 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Juergen Gross <jgross@...e.com>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xensource.com>, <konrad.wilk@...cle.com>,
	<david.vrabel@...rix.com>, <boris.ostrovsky@...cle.com>,
	<daniel.kiper@...cle.com>
Subject: Re: [Xen-devel] [PATCH 2/2] xen: before ballooning hotplugged memory,
 set frames to invalid

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;
    break;

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

Use else here.

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

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