From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 1EE291A1E63 for ; Sat, 5 Sep 2015 04:01:30 +1000 (AEST) Date: Fri, 4 Sep 2015 20:01:22 +0200 From: Jan Stancek To: Nishanth Aravamudan Cc: Michael Ellerman , Wei Yang , Alexey Kardashevskiy , Gavin Shan , Hari Bathini , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, David Gibson Subject: Re: powerpc/powernv/pci-ioda: fix kdump with non-power-of-2 crashkernel= Message-ID: <20150904180108.GA30660@dustball.brq.redhat.com> References: <20150904165938.GL47557@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20150904165938.GL47557@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Sep 04, 2015 at 09:59:38AM -0700, Nishanth Aravamudan wrote: > The 32-bit TCE table initialization relies on the DMA window having a > size equal to a power of 2 (and checks for it explicitly). But > crashkernel= has no constraint that requires a power-of-2 be specified. > This causes the kdump kernel to fail to boot as none of the PCI devices > (including the disk controller) are successfully initialized. > > After this change, the PCI devices successfully set up the 32-bit TCE > table and kdump succeeds. > > Fixes: aca6913f5551 ("powerpc/powernv/ioda2: Introduce helpers to allocate TCE pages") > Signed-off-by: Nishanth Aravamudan > Cc: stable@vger.kernel.org # 4.2 > --- > > Michael, I did this as a follow-on patch to my previous one. If you'd > rather I made a v3 of that patch with the two fixes combined, I can > resend. > > diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c > index f1c74c28e564..73914f4bd1ab 100644 > --- a/arch/powerpc/platforms/powernv/pci-ioda.c > +++ b/arch/powerpc/platforms/powernv/pci-ioda.c > @@ -2084,6 +2084,12 @@ static long pnv_pci_ioda2_setup_default_config(struct pnv_ioda_pe *pe) > */ > const u64 window_size = > min((u64)pe->table_group.tce32_size, memory_hotplug_max()); > + /* > + * crashkernel= specifies the kdump kernel's maximum memory at > + * some offset and there is no guaranteed the result is a power > + * of 2, which will cause errors later. > + */ > + window_size = __rounddown_pow_of_two(window_size); Hi, Just wondering if this won't hide potential alignment issues of "table_group.tce32_size", that now trigger EINVAL down the road and if it wouldn't be safer to round only "memory_hotplug_max()? const __u64 hotplug_max_p2 = __rounddown_pow_of_two(memory_hotplug_max()); const __u64 window_size = min((u64)pe->table_group.tce32_size, hotplug_max_p2); Regards, Jan > > rc = pnv_pci_ioda2_create_table(&pe->table_group, 0, > IOMMU_PAGE_SHIFT_4K,