From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ard Biesheuvel Subject: Re: ARM: KVM/XEN: how should we support virt-what? Date: Thu, 26 Mar 2015 19:50:06 +0100 Message-ID: References: <20150325094440.GB3163@hawk.usersys.redhat.com> <20150326090150.GA3073@hawk.usersys.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefano Stabellini Cc: Wei Huang , Andrew Jones , Ian Campbell , KVM devel mailing list , Marc Zyngier , tim@xen.org"Richard W.M. Jones" , "xen-devel@lists.xen.org" , Christoffer Dall , "kvmarm@lists.cs.columbia.edu" , "linux-arm-kernel@lists.infradead.org" List-Id: xen-devel@lists.xenproject.org On 26 March 2015 at 19:49, Ard Biesheuvel wrote: > On 26 March 2015 at 19:45, Stefano Stabellini > wrote: >> On Thu, 26 Mar 2015, Andrew Jones wrote: >>> On Wed, Mar 25, 2015 at 10:44:42AM +0100, Andrew Jones wrote: >>> > Hello ARM virt maintainers, >>> > >>> > I'd like to start a discussion about supporting virt-what[1]. virt-what >>> > allows userspace to determine if the system it's running on is running >>> > in a guest, and of what type (KVM, Xen, etc.). Despite it being a best >>> > effort tool, see the Caveat emptor in [1], it has become quite a useful >>> > tool, and is showing up in different places, such as OpenStack. If you >>> > look at the code[2], specifically [3], then you'll see how it works on >>> > x86, which is to use the dedicated hypervisor cpuid leaves. I'm >>> > wondering what equivalent we have, or can develop, for arm. >>> > Here are some thoughts; >>> > 0) there's already something we can use, and I just need to be told >>> > about it. >>> > 1) be as similar as possible to x86 by dedicating some currently >>> > undefined sysreg bits. This would take buy-in from lots of parties, >>> > so is not likely the way to go. >>> > 2) create a specific DT node that will get exposed through sysfs, or >>> > somewhere. >>> > 3) same as (2), but just use the nodes currently in mach-virt's DT >>> > as the indication we're a guest. This would just be a heuristic, >>> > i.e. "have virtio mmio" && psci.method == hvc, or something, >>> > and we'd still need a way to know if we're kvm vs. xen vs. ??. >>> > >>> > Thanks, >>> > drew >>> > >>> > [1] http://people.redhat.com/~rjones/virt-what/ >>> > [2] http://git.annexia.org/?p=virt-what.git;a=summary >>> > [3] http://git.annexia.org/?p=virt-what.git;a=blob_plain;f=virt-what-cpuid-helper.c;hb=HEAD >>> >>> Thanks everyone for their responses. So, the current summary seems to >>> be; >>> 1) Xen has both a DT node and an ACPI table, virt-what can learn how >>> to probe those. >>> 2) We don't have anything yet for KVM, and we're reluctant to create a >>> specific DT node. Anyway, we'd still need to address ACPI booted >>> guests some other way. >>> >>> For a short-term, DT-only, approach we could go with a heuristic, one >>> that includes Marc's "if hypervisor node exists, then xen, else kvm" >>> condition. >>> >>> How about SMBIOS for a long-term solution that works for both DT and >>> ACPI? We're not populating SMBIOS for arm guests yet in qemu, but now >>> that AAVMF has fw_cfg, we should be able to. On x86 we already have >>> smbios populated from qemu, although not in a way that allows us to >>> determine kvm vs. xen vs. tcg. >> >> I don't think that SMBIOS works with DT. >> > > SMBIOS works fine with DT ... but it needs UEFI ...