From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: Re: [PATCH v4 10/10] x86: Support compiling out userspace IO (iopl and ioperm) Date: Mon, 03 Nov 2014 11:26:55 -0800 Message-ID: <5457D6FF.5060800@amacapital.net> References: <20141103121049.2f0c81a9@alan.etchedpixels.co.uk> <20141103141357.GC21818@thin> <20141103152748.327032f8@alan.etchedpixels.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20141103152748.327032f8@alan.etchedpixels.co.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: One Thousand Gnomes , Josh Triplett Cc: Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner List-Id: virtualization@lists.linuxfoundation.org On 11/03/2014 07:27 AM, One Thousand Gnomes wrote: >>> This isn't unreasonable but there are drivers with userspace helpers that >>> use iopl/ioperm type functionality where you should be doing a SELECT of >>> X86_IOPORT. The one that comes to mind is the uvesa driver. From a quick >>> scan it may these days be the only mainstream one that needs the select >>> adding. >> >> Should kernel drivers really express dependencies that only their >> (current instances of) corresponding userspace components need? >> Something seems wrong about that. > > uvesafb will always need X86_IOPORT. It's kind of implicit in the design. > I'm not suggesting that fbdev should select X86_IOPORT but in the uvesafb > case at least it's completely useless to have one and not the other. Are there any users of uvesafb at all? Last time I changed that driver, I tried to test it, and I was unable to find a copy of the userspace helper. --Andy > >> IO_BITMAP_LONGS already gets defined to (0/sizeof(long)). And as far as >> I can tell, that would only work for init_tss_io, not anything else. >> Even then, that would only work with a zero-size array left around in >> tss_struct, which doesn't seem appropriate. The remaining ifdefs wrap >> code that GCC could not constant-fold away, and making that code >> constant-foldable seems significantly more invasive than the ifdefs. > > OK >