From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f48.google.com (mail-wg0-f48.google.com [74.125.82.48]) by kanga.kvack.org (Postfix) with ESMTP id BD17C6B0032 for ; Thu, 4 Dec 2014 07:03:19 -0500 (EST) Received: by mail-wg0-f48.google.com with SMTP id y19so22435904wgg.7 for ; Thu, 04 Dec 2014 04:03:19 -0800 (PST) Received: from foss-mx-na.foss.arm.com (foss-mx-na.foss.arm.com. [217.140.108.86]) by mx.google.com with ESMTP id eh2si44355104wjd.149.2014.12.04.04.03.18 for ; Thu, 04 Dec 2014 04:03:18 -0800 (PST) Date: Thu, 4 Dec 2014 12:03:05 +0000 From: Catalin Marinas Subject: Re: [RFC v2] arm:extend the reserved mrmory for initrd to be page aligned Message-ID: <20141204120305.GC17783@e104818-lin.cambridge.arm.com> References: <35FD53F367049845BC99AC72306C23D103D6DB491609@CNBJMBX05.corpusers.net> <20140915113325.GD12361@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140915113325.GD12361@n2100.arm.linux.org.uk> Sender: owner-linux-mm@kvack.org List-ID: To: Russell King - ARM Linux Cc: "Wang, Yalin" , "'linux-mm@kvack.org'" , Will Deacon , "'linux-kernel@vger.kernel.org'" , "'linux-arm-kernel@lists.infradead.org'" , "'linux-arm-msm@vger.kernel.org'" , Peter Maydell On Mon, Sep 15, 2014 at 12:33:25PM +0100, Russell King - ARM Linux wrote: > On Mon, Sep 15, 2014 at 07:07:20PM +0800, Wang, Yalin wrote: > > @@ -636,6 +646,11 @@ static int keep_initrd; > > void free_initrd_mem(unsigned long start, unsigned long end) > > { > > if (!keep_initrd) { > > + if (start == initrd_start) > > + start = round_down(start, PAGE_SIZE); > > + if (end == initrd_end) > > + end = round_up(end, PAGE_SIZE); > > + > > poison_init_mem((void *)start, PAGE_ALIGN(end) - start); > > free_reserved_area((void *)start, (void *)end, -1, "initrd"); > > } > > is the only bit of code you likely need to achieve your goal. > > Thinking about this, I think that you are quite right to align these. > The memory around the initrd is defined to be system memory, and we > already free the pages around it, so it *is* wrong not to free the > partial initrd pages. Actually, I think we have a problem, at least on arm64 (raised by Peter Maydell). There is no guarantee that the page around start/end of initrd is free, it may contain the dtb for example. This is even more obvious when we have a 64KB page kernel (the boot loader doesn't know the page size that the kernel is going to use). The bug was there before as we had poison_init_mem() already (not it disappeared since free_reserved_area does the poisoning). So as a quick fix I think we need the rounding the other way (and in the general case we probably lose a page at the end of initrd): diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 494297c698ca..39fd080683e7 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -335,9 +335,9 @@ void free_initrd_mem(unsigned long start, unsigned long end) { if (!keep_initrd) { if (start == initrd_start) - start = round_down(start, PAGE_SIZE); + start = round_up(start, PAGE_SIZE); if (end == initrd_end) - end = round_up(end, PAGE_SIZE); + end = round_down(end, PAGE_SIZE); free_reserved_area((void *)start, (void *)end, 0, "initrd"); } A better fix would be to check what else is around the start/end of initrd. -- Catalin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org