Date: Fri, 11 Sep 2015 14:14:09 +0100 From: Stefano Stabellini <stefano.stabellini@eu.citrix.com> To: Daniel Kiper <daniel.kiper@oracle.com> Cc: Mark Rutland <mark.rutland@arm.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Shannon Zhao <zhaoshenglong@huawei.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>, "linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>, "Ian.Campbell@citrix.com" <Ian.Campbell@citrix.com>, "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>, "ard.biesheuvel@linaro.org" <ard.biesheuvel@linaro.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "leif.lindholm@linaro.org" <leif.lindholm@linaro.org>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>, "julien.grall@citrix.com" <julien.grall@citrix.com>, "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>, "matt.fleming@intel.com" <matt.fleming@intel.com>, "christoffer.dall@linaro.org" <christoffer.dall@linaro.org>, "jbeulich@suse.com" <jbeulich@suse.com>, "peter.huangpeng@huawei.com" <peter.huangpeng@huawei.com>, "shannon.zhao@linaro.org" <shannon.zhao@linaro.org>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Subject: Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Message-ID: <alpine.DEB.2.02.1509111410180.2672@kaball.uk.xensource.com> In-Reply-To: <20150911124643.GB4530@olila.local.net-space.pl> References: <1441874516-11364-1-git-send-email-zhaoshenglong@huawei.com> <20150910095208.GA29293@leverpostej> <alpine.DEB.2.02.1509101116580.2672@kaball.uk.xensource.com> <20150910112418.GC29293@leverpostej> <alpine.DEB.2.02.1509101223580.2672@kaball.uk.xensource.com> <20150910121514.GE29293@leverpostej> <alpine.DEB.2.02.1509101429480.2672@kaball.uk.xensource.com> <20150910144938.GI29293@leverpostej> <alpine.DEB.2.02.1509101655020.2672@kaball.uk.xensource.com> <20150910162302.GN29293@leverpostej> <20150911124643.GB4530@olila.local.net-space.pl>
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On Fri, 11 Sep 2015, Daniel Kiper wrote: > On Thu, Sep 10, 2015 at 05:23:02PM +0100, Mark Rutland wrote: > > > > C) When you could go: > > > > > > > > DT -> Discover Xen -> Xen-specific stuff -> Xen-specific EFI/ACPI discovery > > > > > > I take you mean discovering Xen with the usual Xen hypervisor node on > > > device tree. I think that C) is a good option actually. I like it. Not > > > sure why we didn't think about this earlier. Is there anything EFI or > > > ACPI which is needed before Xen support is discovered by > > > arch/arm64/kernel/setup.c:setup_arch -> xen_early_init()? > > > > Currently lots (including the memory map). With the stuff to support > > SPCR, the ACPI discovery would be moved before xen_early_init(). > > > > > If not, we could just go for this. A lot of complexity would go away. > > > > I suspect this would still be fairly complex, but would at least prevent > > the Xen-specific EFI handling from adversely affecting the native case. > > > > > > D) If you want to be generic: > > > > EFI -> EFI application -> EFI tables -> ACPI tables -> Xen-specific stuff > > > > \------------------------------------------/ > > > > (virtualize these, provide shims to Dom0, but handle > > > > everything in Xen itself) > > > > > > I think that this is good in theory but could turn out to be a lot of > > > work in practice. We could probably virtualize the RuntimeServices but > > > the BootServices are troublesome. > > > > What's troublesome with the boot services? > > > > What can't be simulated? > > How do you want to access bare metal EFI boot services from dom0 if they > were shutdown long time ago before loading dom0 image? What do you need > from EFI boot services in dom0? That's right. Trying to emulate BootServices after the real ExitBootServices has already been called seems like a very bad plan. I think that whatever interface we come up with, would need to be past ExitBootServices.
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