linux-kernel - [PATCH] xen: actually release memory when shrinking domain

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Message-ID: <4978F4D8.6090706@goop.org>
Date:	Thu, 22 Jan 2009 14:36:08 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	"dan.magenheimer@...cle.com" <dan.magenheimer@...cle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	Stable Kernel <stable@...nel.org>
Subject: [PATCH] xen: actually release memory when shrinking domain

From: Dan Magenheimer <dan.magenheimer@...cle.com>

Fix this:

> It appears that in the upstream balloon driver,
> > the call to HYPERVISOR_update_va_mapping is missing
> > from decrease_reservation.  I think as a result,
> > the balloon driver is eating memory but not
> > releasing it to Xen, thus rendering the balloon
> > driver essentially useless.  (Can be observed via xentop.)

Signed-off-by: Dan Magenheimer <dan.magenheimer@...cle.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 drivers/xen/balloon.c |    5 +++++
 1 file changed, 5 insertions(+)

===================================================================
--- linux-2.6.28/drivers/xen/balloon.c.orig
+++ linux-2.6.28/drivers/xen/balloon.c
@@ -296,6 +296,11 @@
 		frame_list[i] = pfn_to_mfn(pfn);
 
 		scrub_page(page);
+
+		ret = HYPERVISOR_update_va_mapping(
+			(unsigned long)__va(pfn << PAGE_SHIFT),
+			__pte_ma(0), 0);
+		BUG_ON(ret);
 	}
 
 	/* Ensure that ballooned highmem pages don't have kmaps. */


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