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From: Roland Dreier <rdreier@cisco.com>
To: Avi Kivity <avi@redhat.com>
Cc: Glauber Costa <glommer@redhat.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	aliguori@codemonkey.ws, npiggin@suse.de,
	Jeremy Fitzhardinge <jeremy@goop.org>,
	Krzysztof Helt <krzysztof.h1@poczta.fm>
Subject: Re: [PATCH] regression: vmalloc easily fail.
Date: Tue, 28 Oct 2008 14:22:16 -0700	[thread overview]
Message-ID: <ada7i7so1o7.fsf@cisco.com> (raw)
In-Reply-To: <49077E1A.5080105@redhat.com> (Avi Kivity's message of "Tue, 28 Oct 2008 23:03:22 +0200")

 > I'm guessing that the missing comment explains that this is
 > intentional, to trap buffer overflows?

Actually, speaking of comments, it's interesting that
__get_vm_area_node() -- which is called from vmalloc() -- does:

	/*
	 * We always allocate a guard page.
	 */
	size += PAGE_SIZE;

	va = alloc_vmap_area(size, align, start, end, node, gfp_mask);

and alloc_vmap_area() adds another PAGE_SIZE, as the original email
pointed out:

		while (addr + size >= first->va_start && addr + size <= vend) {
			addr = ALIGN(first->va_end + PAGE_SIZE, align);

I wonder if the double padding is causing a problem when things get too
fragmented?

 - R.

  parent reply	other threads:[~2008-10-28 21:22 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-28 22:55 Glauber Costa
2008-10-28 21:03 ` Avi Kivity
2008-10-28 21:09   ` Glauber Costa
2008-10-28 21:22     ` Matias Zabaljauregui
2008-10-28 21:22   ` Roland Dreier [this message]
2008-10-28 21:42     ` Arjan van de Ven
2008-10-28 22:03       ` Roland Dreier
2008-10-28 23:29 ` Nick Piggin
2008-10-29  6:28   ` Avi Kivity
2008-10-29  9:48   ` Glauber Costa
2008-10-29 10:11     ` Nick Piggin
2008-10-29 10:29       ` Avi Kivity
2008-10-29 10:43         ` Nick Piggin
2008-10-29 22:07           ` Glauber Costa
2008-10-30  1:53             ` Nick Piggin
2008-10-30  4:49             ` Nick Piggin
2008-10-30 11:28               ` Glauber Costa
2008-10-31  7:16                 ` Nick Piggin
2008-11-04 17:51                   ` Glauber Costa
2008-11-05  0:21                   ` Glauber Costa
2008-10-30 16:46               ` Matt Mackall
2008-10-30 18:04                 ` Glauber Costa
2008-10-31  2:59                   ` Nick Piggin
2008-11-07 20:37               ` Glauber Costa

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