On 09.02.2026 11:02, Bertrand Marquis wrote: > 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
There have been several "previous" comments there, so I think in this case it may indeed be better ... > Othewise happy to submit a v5 ... if you do this. I'm sorry, it's quite a bit of bike-shedding on "merely" commentary, yet I think we want to avoid misleading people. Jan
