Hi Jan, > On 9 Feb 2026, at 10:45, Jan Beulich <[email protected]> wrote: > > On 09.02.2026 10:11, Roger Pau Monné wrote: >> On Mon, Feb 09, 2026 at 07:30:30AM +0000, Bertrand Marquis wrote: >>> Hi Roger, >>> >>>> On 6 Feb 2026, at 18:25, Roger Pau Monné <[email protected]> wrote: >>>> >>>> On Fri, Feb 06, 2026 at 05:21:44PM +0100, Bertrand Marquis wrote: >>>>> Xen does not provide a Darwin build configuration for selecting >>>>> GNU tool definitions. On macOS, the tools we use are either GNU >>>>> compatible or we only rely on features supported by Mac OS, so >>>>> using the GNU tool definitions is appropriate. >>>>> >>>>> Add config/Darwin.mk to include StdGNU.mk and force >>>>> XEN_COMPILE_ARCH=unknown, ensuring Darwin builds always follow >>>>> the cross-compile path as we depend on the Linux ABI so compiling >>>>> on Mac OS is always a cross compilation case. >>>>> >>>>> An example of how to build the hypervisor for arm64 on Mac OS >>>>> (tools cannot be build for now) using a toolchain from brew: >>>>> - brew install aarch64-elf-gcc aarch64-elf-binutils >>>>> - cd xen >>>>> - make XEN_TARGET_ARCH=arm64 CROSS_COMPILE=aarch64-elf- HOSTCC=clang >>>> >>>> Instead of `cd xen` I would use `make xen ...`. >>> >>> Ack the 'cd xen' line is useless and should be removed. >>> >>>> >>>>> >>>>> Signed-off-by: Bertrand Marquis <[email protected]> >>>> >>>> Acked-by: Roger Pau Monné <[email protected]> >>>> >>>> One comment below. >>>> >>>>> --- >>>>> Changes since v3: >>>>> - set XEN_COMPILE_ARCH to unknown instead of Darwin >>>>> - list binutils as a dependency to install in brew in commit message >>>>> >>>>> Changes since v2: >>>>> - Subject was "xen: Add macOS hypervisor build configuration" >>>>> - Update Darwin.mk comments to more accurate versions (Jan) >>>>> - Remove the build-on-macos help as we have no dependency on anything >>>>> coming from brew anymore and the toolchain can be retrieved by lots of >>>>> other solutions than brew on mac os. Switch to a simple doc in the >>>>> commit message instead >>>>> --- >>>>> config/Darwin.mk | 7 +++++++ >>>>> 1 file changed, 7 insertions(+) >>>>> create mode 100644 config/Darwin.mk >>>>> >>>>> diff --git a/config/Darwin.mk b/config/Darwin.mk >>>>> new file mode 100644 >>>>> index 000000000000..176b27eac676 >>>>> --- /dev/null >>>>> +++ b/config/Darwin.mk >>>>> @@ -0,0 +1,7 @@ >>>>> +# Use GNU tool definitions as the tools we are using are either GNU >>>>> compatible >>>>> +# or we only use features which are supported on Mac OS. >>>>> +include $(XEN_ROOT)/config/StdGNU.mk >>>>> + >>>>> +# Xen uses Linux'es ABI so we are cross compiling on Mac OS. >>>> >>>> Hm, is this actually fully true? What's the Linux ABI exactly here? >>>> >>>> FreeBSD builds Xen natively, and it's not using the Linux ABI. >>>> FreeBSD uses no specific -target to the compiler invocations, and the >>>> linker emulation is set to elf_x86_64_fbsd. >>>> >>>> I think the point here is that the toolchain must support building ELF >>>> objects / images, because that's the binary format supported by Xen. >>>> Whether it's Linux ELF or FreeBSD ELF doesn't make a difference for >>>> standalone environments like the Xen kernel. >>> >>> This file is also use while compiling the tools and for those you definitely >>> to cross compile as they depend on Linux ABI. >> >> I'm not an expert on this at all, but IMO the tools don't depend on >> the Linux ABI at all. Anyone can add the minimal OS-specific bindings >> required for the tools to work on environments different than Linux. >> We currently have {Net,Free}BSD and Linux. In the past we also had >> Solaris, but that has bit rotten. >> >>> Maybe that works on BSD >>> but i doubt this would be the case on mac os. >> >> I doubt we would ever have any need to build an OSX native toolchain, >> as it's unlikely (?) that we will ever get Xen support in the Darwin >> kernel. > > If Darwin has some way to load "modules" (e.g. drivers) into the kernel, it > may in principle be possible to run OSX as a HVM-Dom0, with a Xen driver > loaded separately. That's far fetched, I know. > >>> Maybe we could simplify the sentence to not say anything we are unsure: >>> >>> # Cross compile on Mac OS >>> >>> Tell me if that works for you and i can submit a v5 or this might be >>> possible to >>> fix on commit. >> >> I'm fine with it, I would like to hear Jan's opinion. > > As long as it's clear that all of this is only about building the hypervisor > (which doesn't look to be the case right now beyond the example given in the > commit message, which may be taken as really only an example), that's okay > [1]. I'd still prefer to mention the SVR4 ABI here, though, to at least > somewhat explain the "always cross" aspect. > > I can make edits while committing, but I'm unsure whether that's wanted in > this case.
I would suggest: Cross compile on Mac OS, only hypervisor build has been tested, no tools Please do the following edits on commit if that's ok for you : - remove 'cd xen' from commit message - use previous comment in Darwin.mk Othewise happy to submit a v5 Cheers Bertrand > > Jan > > [1] Yet better might be if we refused to build other than the hypervisor. > I'm unsure though how easy it would be to achieve that in an at least > halfway tidy manner.
