From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from flmx07.ccur.com ([12.192.68.12]) by bombadil.infradead.org with esmtps (Exim 4.69 #1 (Red Hat Linux)) id 1N3FyC-0002wC-6I for kexec@lists.infradead.org; Wed, 28 Oct 2009 21:22:20 +0000 Message-ID: <4AE8B612.9080103@ccur.com> Date: Wed, 28 Oct 2009 16:22:26 -0500 From: John Blackwood MIME-Version: 1.0 Subject: Re: Kdump issue with percpu_alloc=lpage List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: kexec-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Vivek Goyal Cc: Tejun Heo , "kexec@lists.infradead.org" > Subject: Re: Kdump issue with percpu_alloc=lpage > From: Vivek Goyal > Date: Tue, 27 Oct 2009 15:24:14 -0400 > To: "Blackwood, John" > CC: Tejun Heo , "kexec@lists.infradead.org" > > > > The lpage allocator is gone in the latest tree and only "embed" and > > > "page" allocators are there. The only difference between the two is > > > that the embed one will put the first chunk inside the linearly mapped > > > area which in turn means that __pa() would work on static percpu > > > variables and some of dynamic ones but from the second chunk on and > > > for the page allocator, the percpu addresses will be remapped into > > > vmalloc area and behaves just like any other vmalloc address meaning > > > that the physical page can be determined using vmalloc_to_page(). So, > > > something like the following should work, > > > > > > v = per_cpu_ptr(crash_notes, cpunum); > > > if (v < VMALLOC_START || v >= VMALLOC_END) > > > p = __pa(v); > > > else > > > p = page_to_phys(vmalloc_to_page(v)); > > > > > > For the now removed lpage, it would be a bit difficult and we'll > > > probably need to add a dedicated function to percpu to determine the > > > physical address. Hmmm... probably the right thing to do is to add > > > such function so that the user can simply call percpu_to_phys() > > > regardless of address? > > > > Hi Tejun, > > > > Just my 2 cent's worth... > > > > I like the idea of having a percpu_to_phys() function that others can > > call so that such detail are localized... and this also would tend to > > be maintained better over time, since it would be more visible being > > located near where the percpu support is implmented. > > > > Thank you for the information. > > Thanks Tejun. percpu_to_phys() makes sense to me also. John, would you > like to post a patch for this. Hi Vivek, I'm probably not really NUMA/vm savy enough to attempt a patch for approval at LKML. But maybe someone else more qualified can take up the cause. Thanks. _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec