From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: From: Michael Ellerman To: Bjorn Helgaas , Yongji Xie Cc: bhelgaas@google.com, linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, alex.williamson@redhat.com, gwshan@linux.vnet.ibm.com, aik@ozlabs.ru, benh@kernel.crashing.org, paulus@samba.org, zhong@linux.vnet.ibm.com Subject: Re: [PATCH v9 2/3] PCI: Add a macro to set default alignment for all PCI devices In-Reply-To: <20170323205342.GB23612@bhelgaas-glaptop.roam.corp.google.com> References: <1487141106-2503-1-git-send-email-xyjxie@linux.vnet.ibm.com> <1487141106-2503-3-git-send-email-xyjxie@linux.vnet.ibm.com> <20170323205342.GB23612@bhelgaas-glaptop.roam.corp.google.com> Date: Mon, 27 Mar 2017 21:17:37 +1100 Message-ID: <8737dzf2gu.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain List-ID: Bjorn Helgaas writes: > > I don't know how powerpc kernels are built: can you build a kernel > that will run on PowerNV as well as on different powerpc systems? Yes you can. But there are some restrictions. You can only build a 64-bit OR a 32-bit kernel. And within 64-bit you can only build a *kernel* for the "server architecture (~= IBM CPUs)" or the "embedded architecture (Freescale/NXP)". So in practice you can build a 64-bit kernel that supports: - powernv (bare metal on IBM server chips) - pseries (virtualised on IBM server chips or qemu) - powermac (Apple G5s) - pasemi (long dead but still used by some Amiga folks?) - Cell/PS3 (also long dead) > If so, is it acceptable to force that kernel to user 64K alignment even > when it's running on non-PowerNV systems? Probably, but I'm not sure TBH. Benh will know, I'll try and get his attention. cheers