From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from kirsty.vergenet.net ([202.4.237.240]) by bombadil.infradead.org with esmtp (Exim 4.69 #1 (Red Hat Linux)) id 1O03EE-0002lP-Fn for kexec@lists.infradead.org; Fri, 09 Apr 2010 01:41:52 +0000 Date: Fri, 9 Apr 2010 11:41:47 +1000 From: Simon Horman Subject: Re: [PATCH] kexec: fix 64Gb limit on x86 w/ PAE Message-ID: <20100409014144.GA25947@verge.net.au> References: <20100408164644.GB16868@hmsreliant.think-freely.org> <20100408223245.GA4795@verge.net.au> <20100409012439.GA2060@localhost.localdomain> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20100409012439.GA2060@localhost.localdomain> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: kexec-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Neil Horman Cc: anderson@redhat.com, kexec@lists.infradead.org, vgoyal@redhat.com On Thu, Apr 08, 2010 at 09:24:39PM -0400, Neil Horman wrote: > On Fri, Apr 09, 2010 at 08:32:48AM +1000, Simon Horman wrote: > > On Thu, Apr 08, 2010 at 12:46:44PM -0400, Neil Horman wrote: > > > Fix up x86 kexec to exclude memory on i686 kernels beyond 64GB limit > > > > > > We found a problem recently on x86 systems. If a 32 bit PAE enabled system > > > contains more then 64GB of physical ram, the kernel will truncate the max_pfn > > > value to 64GB. Unfortunately it still leaves all the physical memory regions > > > present in /proc/iomem. Since kexec builds its elf headers based on > > > /proc/iomem the elf headers indicate the size of memory is larger than what the > > > kernel is willing to address. The result is that, during a copy of > > > /proc/vmcore, a read will return -EFAULT when the requested offset is beyond the > > > 64GB range, leaving the seemingly truncated vmcore useless, as the elf headers > > > indicate memory beyond what the file contains. > > > > > > The fix for it is pretty straightforward, just ensure that, when on x86 systems, > > > we don't record any entries in the memory_range array that cross the 64Gb mark. > > > This keeps us in line with the kernel and lets the copy finish sucessfully, > > > providing a workable core > > > > Hi Neil, > > > > This seems reasonable to me. > > > > > Tested successfully by myself > > > Originally-authored-by: Dave Anderson > > > Signed-off-by: Neil Horman > > > > > > diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c > > > index 9d37442..85879a9 100644 > > > --- a/kexec/arch/i386/crashdump-x86.c > > > +++ b/kexec/arch/i386/crashdump-x86.c > > > @@ -114,6 +114,15 @@ static int get_crash_memory_ranges(struct memory_range **range, int *ranges, > > > if (end <= 0x0009ffff) > > > continue; > > > > > > + /* > > > + * Exclude any segments starting at or beyond 64GB, and > > > + * restrict any segments from ending at or beyond 64GB. > > > + */ > > > + if (start >= 0x1000000000) > > > + continue; > > > + if (end >= 0x1000000000) > > > + end = 0xfffffffff; > > > + > > > > Nit picking... > > > > Might it be better to use 0xfffffffff (or 0x1000000000) consistently? > > > > if (start > 0xfffffffff) > > continue; > > if (end > 0xfffffffff) > > end = 0xfffffffff; > > > Not sure what you mean by consistent here? It seems we are using it > consistently in this patch. Or are you referring to updating the function as a > whole? Sorry, yes they are consistent. And I believe the code you posted is correct. What I meant was that as 0xfffffffff + 1 = 0x1000000000, the code could either only use 0xfffffffff or only use 0x1000000000. Which seems to make things slightly more obvious when reading the code. > > Or even make 0xfffffffff (or 0x1000000000) a #define ? > Yeah, that makes sense. If you can clarify your above point on consistency, I > can repost. > > thanks > Neil > > > > > > crash_memory_range[memory_ranges].start = start; > > > crash_memory_range[memory_ranges].end = end; > > > crash_memory_range[memory_ranges].type = type; > > > > > > > > > _______________________________________________ > > > kexec mailing list > > > kexec@lists.infradead.org > > > http://lists.infradead.org/mailman/listinfo/kexec > > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec