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To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Don.Brace@microchip.com, Sergei Trofimovich <slyfox@gentoo.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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        Scott.Benesh@microchip.com, Scott.Teel@microchip.com,
        thenzl@redhat.com,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Subject: Re: [PATCH] hpsa: fix boot on ia64 (atomic_t alignment)
From:   "Martin K. Petersen" <martin.petersen@oracle.com>
Organization: Oracle Corporation
Message-ID: <yq1zgz21rkz.fsf@ca-mkp.ca.oracle.com>
References: <5532f9ab-7555-d51b-f4d5-f9b72a61f248@redhat.com>
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Date:   Tue, 16 Mar 2021 22:25:30 -0400
In-Reply-To: <CAK8P3a3JYmhbN3TXB2cWGfXGKgsUa9Hg=ZvWckTaL_31OMgbtQ@mail.gmail.com>
        (Arnd Bergmann's message of "Tue, 16 Mar 2021 19:28:22 +0100")
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Arnd,

> Actually that still feels wrong: the annotation of the struct is to
> pack every member, which causes the access to be done in byte units on
> architectures that do not have hardware unaligned load/store
> instructions, at least for things like atomic_read() that does not go
> through a cmpxchg() or ll/sc cycle.

> This change may fix itanium, but it's still not correct. Other
> architectures would have already been broken before the recent change,
> but that's not a reason against fixing them now.

I agree. I understand why there are restrictions on fields consumed by
the hardware. But for fields internal to the driver the packing doesn't
make sense to me.

-- 
Martin K. Petersen	Oracle Linux Engineering