Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   David Laight <David.Laight@ACULAB.COM>
To:     'Johannes Berg' <johannes@sipsolutions.net>,
        "linux-um@lists.infradead.org" <linux-um@lists.infradead.org>
CC:     "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Johannes Berg <johannes.berg@intel.com>
Subject: RE: [PATCH] um: don't use CONFIG_X86_{32,64} symbols on x86
Thread-Topic: [PATCH] um: don't use CONFIG_X86_{32,64} symbols on x86
Thread-Index: AQHXn9SPoN4pW3t210qkf8kng5akKquR+fUg
Date:   Fri, 3 Sep 2021 08:27:24 +0000
Message-ID: <f177f8b287f14c93b04542d7ab4a8dfd@AcuMS.aculab.com>
References: <20210902102750.1ddfef4c1915.Icb5c49998c55b87c8584d46894c01b114ae2e661@changeid>
In-Reply-To: <20210902102750.1ddfef4c1915.Icb5c49998c55b87c8584d46894c01b114ae2e661@changeid>
Accept-Language: en-GB, en-US
MIME-Version: 1.0
Content-Language: en-US
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8BIT
Precedence: bulk

From: Johannes Berg
> Sent: 02 September 2021 09:28
> 
> The CONFIG_X86_32 and CONFIG_X86_64 symbols are used by
> both "real" x86 architecture builds and ARCH=um today.
> However, clearly most people and places in the code are
> treating it as the architecture Kconfig (technically
> that's just CONFIG_X86) and use it to indicate that the
> architecture is X86 in 32- or 64-bit flavour.
> 
> This has caused a fair amount of issues in the past,
> for example drivers not building because use x86 macros
> or similar under CONFIG_X86_{32,64} ifdef, and then we
> find build reports and add "!UML" to their Kconfig etc.
> 
> However, this is error-prone and a kind of whack-a-mole
> game, even with the build bots reporting things.

I suspect you've just changed the 'mole'.

You've now got lots of lines like:

#if defined(CONFIG_X86_64) || defined(CONFIG_X86_64_UML)

Missing off the UML define is going to cause the 32bit code
to get compiled by mistake - which is likely to be more
confusing that the places where you need to do special 'stuff'
for UML.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)