Re: [PATCH v4] arm64: Change type of hsr, cpsr, spsr_el1 to uint64_t

From: Julien Grall <julien@xen.org>
To: Michal Orzel <michal.orzel@arm.com>, Olaf Hering <olaf@aepfle.de>
Cc: xen-devel@lists.xenproject.org,
	Stefano Stabellini <sstabellini@kernel.org>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	Ian Jackson <iwj@xenproject.org>, Jan Beulich <jbeulich@suse.com>,
	Wei Liu <wl@xen.org>, Tamas K Lengyel <tamas@tklengyel.com>,
	Alexandru Isaila <aisaila@bitdefender.com>,
	Petre Pircalabu <ppircalabu@bitdefender.com>,
	bertrand.marquis@arm.com
Subject: Re: [PATCH v4] arm64: Change type of hsr, cpsr, spsr_el1 to uint64_t
Date: Tue, 6 Jul 2021 13:52:45 +0100	[thread overview]
Message-ID: <a640cbcc-1fff-57de-ae4b-a782d99e6b42@xen.org> (raw)
In-Reply-To: <cc4c56cf-4f3a-46d5-ad9c-05596badee70@arm.com>

Hi,

On 06/07/2021 13:50, Michal Orzel wrote:
> 
> 
> On 06.07.2021 14:31, Julien Grall wrote:
>>
>>
>> On 06/07/2021 13:30, Michal Orzel wrote:
>>> Hi,
>>>
>>> On 06.07.2021 14:00, Olaf Hering wrote:
>>>> Am Mon,  5 Jul 2021 08:39:52 +0200
>>>> schrieb Michal Orzel <michal.orzel@arm.com>:
>>>>
>>>>> Modify type of hsr, cpsr, spsr_el1 to uint64_t.
>>>>
>>>> I think this is now commit 918b8842a852e0e7446286f546724b1c63c56c66, which fails to build:
>>>>
>>>> ...
>>>> diff -u reference.size tmp.size
>>>> --- reference.size      2021-06-29 10:50:32.237518309 +0200
>>>> +++ tmp.size    2021-07-06 13:58:19.052592351 +0200
>>>> @@ -4,8 +4,8 @@
>>>>    start_info                |       -       -    1112    1168
>>>>    trap_info                 |       -       -       8      16
>>>>    cpu_user_regs             |       -       -      68     200
>>>> -vcpu_guest_core_regs      |     304     304       -       -
>>>> -vcpu_guest_context        |     344     344    2800    5168
>>>> +vcpu_guest_core_regs      |     312     312       -       -
>>>> +vcpu_guest_context        |     352     352    2800    5168
>>>>    arch_vcpu_info            |       0       0      24      16
>>>>    vcpu_time_info            |      32      32      32      32
>>>>    vcpu_info                 |      48      48      64      64
>>>> gmake[2]: *** [Makefile:24: check-headers] Error 1
>>>>
>>>> osstest may catch this error as well.
>>>>
>>>> Olaf
>>>>
>>>
>>> Where does this report come from so that I can investigate it?
>>> Locally I can build this patch on arm64,arm32,x86 without any issues.
>>
>> This is coming from the tools/include/xen-foreign. I could reproduce it with a:
>>
>> make tools
>>
>> I am currently writing a patch for it. I will send it once I have tested it.
>>
>> Cheers,
>>
>>>
>>> Cheers,
>>> Michal
>>>
>>
> 
> As far as I understand this checker, it is all about the size of these structures.
> What is the reason that the size of them cannot change?
Those structures are meant to be part of the stable ABI. So you would 
break compatibility if the structure size changed across Xen version.

However, we know that vcpu_guest_core_regs and vcpu_guest_context are 
not part of the stable ABI on Arm. However, the tools doesn't understand 
that...

Cheers,

-- 
Julien Grall