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Re: [PATCH 3/5] build: arm64: provide -target and -march if using clang
- To: Julien Grall <julien@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 2 Dec 2024 08:52:12 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>
- Delivery-date: Mon, 02 Dec 2024 07:52:22 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 30.11.2024 18:15, Julien Grall wrote:
> On 29/11/2024 22:12, Volodymyr Babchuk wrote:
>> Jan Beulich <jbeulich@xxxxxxxx> writes:
>>> On 29.11.2024 02:49, Volodymyr Babchuk wrote:
>>>> --- a/config/arm64.mk
>>>> +++ b/config/arm64.mk
>>>> @@ -5,6 +5,10 @@ CONFIG_XEN_INSTALL_SUFFIX :=
>>>>
>>>> CFLAGS += #-marm -march= -mcpu= etc
>>>>
>>>> +ifeq ($(clang),y)
>>>> +CFLAGS += -target aarch64 -march=armv8-a
>>>> +endif
>>>
>>> Why is this dependent on (just?) $(clang), not (also?) $(llvm)?
>>
>> Because this parameter is handled by clang only. There is no harm in
>> providing it explicitly. When building on arm64, value of this parameter
>> will match the default value for the platform. When building on x86, we
>> need to tell clang that it should generate arm64 code anyways. There is
>> no reason in trying to make ARM build with x86 instruction set.
>>
>>> Also
>>> this affects both toolstack builds and hypervisor. Is applying -march
>>> like this actually appropriate for the toolstack?
>>
>> This is a good question. I can't see why this can't be appropriate for
>> toolstack. I.e. what bad can happen when building the toolstack.
>
> In the future, we may want to build the tools for Armv8-M. So I think
> the -march should also applies for the toolstack.
Perhaps I don't know enough of the Arm world, but: Wouldn't it be possible
to build a tool stack suitable for a wide range for Arm64 flavors, while
requiring more targeted hypervisor binaries?
Jan
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