Date: Thu, 10 Sep 2015 17:23:02 +0100 From: Mark Rutland <mark.rutland@arm.com> To: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Cc: 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>, "daniel.kiper@oracle.com" <daniel.kiper@oracle.com> Subject: Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Message-ID: <20150910162302.GN29293@leverpostej> In-Reply-To: <alpine.DEB.2.02.1509101655020.2672@kaball.uk.xensource.com> 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>
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> > 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? > > E) Partially-generic option: > > EFI -> EFI application -> Xen detected by registered GUID -> Xen-specific EFI bootloader stuff -> OS in Xen-specific configuration > > > > > > > > > In any case this should be separate from the shim ABI discussion. > > > > > > > > I disagree; I think this is very much relevant to the ABI discussion. > > > > That's not to say that I insist on a particular approach, but I think > > > > that they need to be considered together. > > > > > > Let's suppose Xen didn't expose any RuntimeServices at all, would that > > > make it easier to discuss about the EFI stub parameters? > > > > It would simply the protocol specific to Xen, certainly. > > > > > In the grant scheme of things, they are not that important, as Ian > > > wrote what is important is how to pass the RSDP. > > > > Unfortunately we're still going to have to care about this eventually, > > even if for something like kexec. So we still need to spec out the state > > of things if this is going to be truly generic. > > Fair enough. My position is that if we restrict this to RuntimeServices, > it might be possible, but I still prefer C). Regardless of what we do we still need a well-defined state here, which brings us back to the initial problem eventually. Thanks, Mark.
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