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Date: Fri, 24 Feb 2017 10:00:33 -0500 From: Adan Hawthorn <adanhawthorn@...il.com> To: Joe Perches <joe@...ches.com> Cc: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de>, Andrew Morton <akpm@...ux-foundation.org>, Brian Gerst <brgerst@...il.com>, Chris Metcalf <cmetcalf@...lanox.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Paolo Bonzini <pbonzini@...hat.com>, Liang Z Li <liang.z.li@...el.com>, Masami Hiramatsu <mhiramat@...nel.org>, Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>, Jonathan Corbet <corbet@....net>, "Michael S. Tsirkin" <mst@...hat.com>, Paul Gortmaker <paul.gortmaker@...driver.com>, Vlastimil Babka <vbabka@...e.cz>, Chen Yucong <slaoub@...il.com>, Alexandre Julliard <julliard@...ehq.org>, Stas Sergeev <stsp@...t.ru>, Fenghua Yu <fenghua.yu@...el.com>, "Ravi V. Shankar" <ravi.v.shankar@...el.com>, Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org, x86@...nel.org, linux-msdos@...r.kernel.org, wine-devel@...ehq.org, Adam Buchbinder <adam.buchbinder@...il.com>, Colin Ian King <colin.king@...onical.com>, Lorenzo Stoakes <lstoakes@...il.com>, Qiaowei Ren <qiaowei.ren@...el.com> Subject: Re: [PATCH v4 01/17] x86/mpx: Do not use SIB index if index points to R/ESP On Thu, Feb 23, 2017 at 9:33 PM, Joe Perches <joe@...ches.com> wrote: > On Thu, 2017-02-23 at 14:17 -0800, Ricardo Neri wrote: >> On Thu, 2017-02-23 at 08:24 +0100, Peter Zijlstra wrote: >> > On Wed, Feb 22, 2017 at 10:36:50PM -0800, Ricardo Neri wrote: >> > > + /* >> > > + * A negative offset generally means a error, except >> > > + * -EDOM, which means that the contents of the register >> > > + * should not be used as index. >> > > + */ >> > > if (indx_offset < 0) >> > > - goto out_err; >> > > + if (indx_offset == -EDOM) >> > > + indx = 0; >> > > + else >> > > + goto out_err; >> > > + else >> > > + indx = regs_get_register(regs, indx_offset); >> > >> > Kernel coding style requires more brackets than are strictly required by >> > C, any block longer than 1 line needs then. Also, if one leg of a >> > conditional needs them, then they should be on both legs. >> > >> > Your code has many such instances, please change them all. >> >> Will do. Sorry for the noise. These instances escaped the checkpatch >> script. > > Also, this code would read better with the inner test > reversed or done first > > if (indx_offset < 0) { > if (indx_offset != -EDOM) > goto out_err; > indx = 0; > } else { > indx = regs_get_register(etc...) > } > > or > if (indx_offset == -EDOM) > indx = 0; > else if (indx_offset < 0) > goto err; Or, goto out_err; > else > indx = regs_get_register(etc...) > > The compiler should generate the same code in any > case, but either could improve reader understanding. Also, it may be a tweak more efficient to handle the most likely runtime case in the conditional stack first (whichever that may be).
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