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From: Robin Murphy <robin.murphy@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	kvmarm <kvmarm@lists.cs.columbia.edu>,
	Android Kernel Team <kernel-team@android.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: Work around broken GCC handling of "S" constraint
Date: Mon, 7 Dec 2020 19:22:01 +0000	[thread overview]
Message-ID: <6e7ecff2-5014-216d-cc0a-6f653dfb3c39@arm.com> (raw)
In-Reply-To: <87360h5tf7.wl-maz@kernel.org>

On 2020-12-07 19:04, Marc Zyngier wrote:
> Hi Robin,
> 
> On Mon, 07 Dec 2020 18:42:23 +0000,
> Robin Murphy <robin.murphy@arm.com> wrote:
>>
>> On 2020-12-07 17:47, Ard Biesheuvel wrote:
>>> On Mon, 7 Dec 2020 at 18:41, Marc Zyngier <maz@kernel.org> wrote:
>>>>
>>>> On 2020-12-07 17:19, Ard Biesheuvel wrote:
>>>>> (resend with David's email address fixed)
>>>>
>>>> Irk. Thanks for that.
>>>>
>>>>>>> +#ifdef CONFIG_CC_HAS_BROKEN_S_CONSTRAINT
>>>>>>> +#define SYM_CONSTRAINT "i"
>>>>>>> +#else
>>>>>>> +#define SYM_CONSTRAINT "S"
>>>>>>> +#endif
>>>>>>> +
>>>>>>
>>>>>> Could we just check GCC_VERSION here?
>>>>
>>>> I guess we could. But I haven't investigated which exact range of
>>>> compiler is broken (GCC 6.3 seems fixed, but that's the oldest
>>>> I have apart from the offending 4.9).
>>>>
>>>
>>> I tried 5.4 on godbolt, and it seems happy. And the failure will be
>>> obvious, so we can afford to get it slightly wrong and refine it
>>> later.
>>
>> FWIW the Linaro 14.11, 15.02 and 15.05 releases of GCC 4.9.3 seem to
>> build rc7 without complaint. The only thing older that I have to hand
>> is Ubuntu's GCC 4.8.4, which Kbuild chokes on entirely now.
> 
> Can you try kvmarm/next? David's PSCI relay is breaking badly here.

Ah, gotcha... Yes, they're all falling over on that :(

The 15.08 release of 5.1.1 is happy though, so Ard's probably right 
about generalising it to 4.x.

Cheers,
Robin.
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Robin Murphy <robin.murphy@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	kvmarm <kvmarm@lists.cs.columbia.edu>,
	David Brazdil <dbrazdil@google.com>,
	Android Kernel Team <kernel-team@android.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: Work around broken GCC handling of "S" constraint
Date: Mon, 7 Dec 2020 19:22:01 +0000	[thread overview]
Message-ID: <6e7ecff2-5014-216d-cc0a-6f653dfb3c39@arm.com> (raw)
In-Reply-To: <87360h5tf7.wl-maz@kernel.org>

On 2020-12-07 19:04, Marc Zyngier wrote:
> Hi Robin,
> 
> On Mon, 07 Dec 2020 18:42:23 +0000,
> Robin Murphy <robin.murphy@arm.com> wrote:
>>
>> On 2020-12-07 17:47, Ard Biesheuvel wrote:
>>> On Mon, 7 Dec 2020 at 18:41, Marc Zyngier <maz@kernel.org> wrote:
>>>>
>>>> On 2020-12-07 17:19, Ard Biesheuvel wrote:
>>>>> (resend with David's email address fixed)
>>>>
>>>> Irk. Thanks for that.
>>>>
>>>>>>> +#ifdef CONFIG_CC_HAS_BROKEN_S_CONSTRAINT
>>>>>>> +#define SYM_CONSTRAINT "i"
>>>>>>> +#else
>>>>>>> +#define SYM_CONSTRAINT "S"
>>>>>>> +#endif
>>>>>>> +
>>>>>>
>>>>>> Could we just check GCC_VERSION here?
>>>>
>>>> I guess we could. But I haven't investigated which exact range of
>>>> compiler is broken (GCC 6.3 seems fixed, but that's the oldest
>>>> I have apart from the offending 4.9).
>>>>
>>>
>>> I tried 5.4 on godbolt, and it seems happy. And the failure will be
>>> obvious, so we can afford to get it slightly wrong and refine it
>>> later.
>>
>> FWIW the Linaro 14.11, 15.02 and 15.05 releases of GCC 4.9.3 seem to
>> build rc7 without complaint. The only thing older that I have to hand
>> is Ubuntu's GCC 4.8.4, which Kbuild chokes on entirely now.
> 
> Can you try kvmarm/next? David's PSCI relay is breaking badly here.

Ah, gotcha... Yes, they're all falling over on that :(

The 15.08 release of 5.1.1 is happy though, so Ard's probably right 
about generalising it to 4.x.

Cheers,
Robin.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-12-07 19:22 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-07 15:43 [PATCH] arm64: Work around broken GCC handling of "S" constraint Marc Zyngier
2020-12-07 15:43 ` Marc Zyngier
2020-12-07 17:17 ` Ard Biesheuvel
2020-12-07 17:17   ` Ard Biesheuvel
2020-12-07 17:19   ` Ard Biesheuvel
2020-12-07 17:19     ` Ard Biesheuvel
2020-12-07 17:41     ` Marc Zyngier
2020-12-07 17:41       ` Marc Zyngier
2020-12-07 17:47       ` Ard Biesheuvel
2020-12-07 17:47         ` Ard Biesheuvel
2020-12-07 18:42         ` Robin Murphy
2020-12-07 18:42           ` Robin Murphy
2020-12-07 19:04           ` Marc Zyngier
2020-12-07 19:04             ` Marc Zyngier
2020-12-07 19:22             ` Robin Murphy [this message]
2020-12-07 19:22               ` Robin Murphy

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