From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f43.google.com (mail-pa0-f43.google.com [209.85.220.43]) by kanga.kvack.org (Postfix) with ESMTP id 416D36B006C for ; Fri, 5 Dec 2014 12:07:58 -0500 (EST) Received: by mail-pa0-f43.google.com with SMTP id kx10so1038186pab.16 for ; Fri, 05 Dec 2014 09:07:58 -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 q3si38043759pdp.113.2014.12.05.09.07.54 for ; Fri, 05 Dec 2014 09:07:55 -0800 (PST) Date: Fri, 5 Dec 2014 17:07:45 +0000 From: Catalin Marinas Subject: Re: [RFC v2] arm:extend the reserved mrmory for initrd to be page aligned Message-ID: <20141205170745.GA31222@e104818-lin.cambridge.arm.com> References: <35FD53F367049845BC99AC72306C23D103D6DB491609@CNBJMBX05.corpusers.net> <20140915113325.GD12361@n2100.arm.linux.org.uk> <20141204120305.GC17783@e104818-lin.cambridge.arm.com> <20141205120506.GH1630@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141205120506.GH1630@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Will Deacon Cc: Russell King - ARM Linux , "Wang, Yalin" , "'linux-mm@kvack.org'" , "'linux-kernel@vger.kernel.org'" , "'linux-arm-kernel@lists.infradead.org'" , "'linux-arm-msm@vger.kernel.org'" , Peter Maydell On Fri, Dec 05, 2014 at 12:05:06PM +0000, Will Deacon wrote: > On Thu, Dec 04, 2014 at 12:03:05PM +0000, Catalin Marinas wrote: > > 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. > > Care to submit this as a proper patch? We should at least fix Peter's issue > before doing things like extending headers, which won't work for older > kernels anyway. Quick fix is the revert of the whole patch, together with removing PAGE_ALIGN(end) in poison_init_mem() on arm32. If Russell is ok with this patch, we can take it via the arm64 tree, otherwise I'll send you a partial revert only for the arm64 part. -------------8<-----------------------