Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751616Ab3IFOKQ (ORCPT ); Fri, 6 Sep 2013 10:10:16 -0400 Received: from fw-tnat.cambridge.arm.com ([217.140.96.21]:50224 "EHLO cam-smtp0.cambridge.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751299Ab3IFOKO (ORCPT ); Fri, 6 Sep 2013 10:10:14 -0400 Date: Fri, 6 Sep 2013 15:09:21 +0100 From: Catalin Marinas To: Ian Campbell Cc: Stefano Stabellini , "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "konrad.wilk@oracle.com" Subject: Re: [PATCH v5 05/13] xen/arm,arm64: move Xen initialization earlier Message-ID: <20130906140921.GD1946@arm.com> References: <1377801154-29215-5-git-send-email-stefano.stabellini@eu.citrix.com> <20130905162026.GJ11887@arm.com> <1378457939.14745.73.camel@kazak.uk.xensource.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1378457939.14745.73.camel@kazak.uk.xensource.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2876 Lines: 71 On Fri, Sep 06, 2013 at 09:58:59AM +0100, Ian Campbell wrote: > On Thu, 2013-09-05 at 17:59 +0100, Stefano Stabellini wrote: > > On Thu, 5 Sep 2013, Catalin Marinas wrote: > > > On Thu, Aug 29, 2013 at 07:32:26PM +0100, Stefano Stabellini wrote: > > > > Move Xen initialization earlier, before any DMA requests can be made. > > > > > > > > Signed-off-by: Stefano Stabellini > > > > > > I guess you should cc the corresponding maintainers here. > > > > Thanks for the reminder, I'll do that. > > > > > > > > arch/arm/include/asm/xen/hypervisor.h | 8 ++++++++ > > > > arch/arm/kernel/setup.c | 2 ++ > > > > arch/arm/xen/enlighten.c | 21 ++++++++++++++------- > > > > arch/arm64/kernel/setup.c | 2 ++ > > > > 4 files changed, 26 insertions(+), 7 deletions(-) > > > > > > [...] > > > > > > > --- a/arch/arm64/kernel/setup.c > > > > +++ b/arch/arm64/kernel/setup.c > > > > @@ -53,6 +53,7 @@ > > > > #include > > > > #include > > > > #include > > > > +#include > > > > > > > > unsigned int processor_id; > > > > EXPORT_SYMBOL(processor_id); > > > > @@ -267,6 +268,7 @@ void __init setup_arch(char **cmdline_p) > > > > unflatten_device_tree(); > > > > > > > > psci_init(); > > > > + xen_early_init(); > > > > > > So Xen guests don't have any hope for single Image? Basically you set > > > dma_ops unconditionally in xen_early_init(), even if the kernel is not > > > intended to run under Xen. > > > > That should not happen: if we are not running on Xen xen_early_init > > returns early, before calling xen_mm_init. > > x96 has a call to init_hypervisor_platform() at approximately this > location, which detects and calls the init function for any of Xen, KVM, > hyperv and vmware. I would rather have a core_initcall(xen_early_init()) if possible, rather than hard-coded calls in setup_arch(). This early stuff is DT-driven, so in theory you don't need a specific xen call. The only thing is that you end up with swiotlb_init() and 64MB wasted if the Xen guest does not plan to use them. > I guess only Xen and KVM are currently relevant on Linux ARM(64), so > perhaps adding similar infrastructure on ARM would be overkill at this > point. I don't know if KVM needs such an early C-land hook, I suppose > it needs it even earlier so it can set up the hyp mode trampoline from > head.S? head.S installs a Hyp stub if it starts in that mode and then forget about. Later when KVM is initialised it installs its own code by doing an HVC call. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/