From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacob Pan Subject: Re: [PATCH v7 0/5] Add Intel IOMMU debugfs support Date: Mon, 19 Mar 2018 09:37:14 -0700 Message-ID: <20180319093714.3afe698b@jacob-builder> References: <1517619001-148586-1-git-send-email-sohil.mehta@intel.com> <20180213140303.42mbzfxpypljy37l@8bytes.org> <20180213214002.GA27066@otc-nc-03> <20180213145332.35c73eda@jacob-builder> <20180215095337.fccoozdclfnbepi4@8bytes.org> <20180215083811.3ec86e49@jacob-builder> <20180315131854.s6xmltsvsysublcw@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180315131854.s6xmltsvsysublcw-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Joerg Roedel Cc: Ravi V Shankar , "Raj, Ashok" , Fenghua Yu , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andy Shevchenko , David Woodhouse , Gayatri Kammela List-Id: iommu@lists.linux-foundation.org On Thu, 15 Mar 2018 14:18:54 +0100 Joerg Roedel wrote: > On Thu, Feb 15, 2018 at 08:38:11AM -0800, Jacob Pan wrote: > > Just wondering if your concern is on the implementation or the > > debugfs idea in general. Perhaps have some common IOMMU debugfs? > > My concern mainly is that we add interfaces which reveal > potentially security relevant information I don;t think security is any worse than existing kernel page table in debugfs. i.e. /sys/kernel/debug/page_tables This is a debug feature. > to user-space and that tools > come up using it so that this also becomes kABI and we can't easily > change it anymore and this whole stuff turns into a maintence > nightmare. > Agreed, perhaps we can address that by only dumping user readable data which avoid having a parser tool that relies on stable kABI? > So that is definitly not something I'd like to see enabled in the > distros, and its better to avoid it at all and search for better ways > to debug upcoming issues. > We can make it "def_bool n" so only used by advanced customers who can recompile kernel. > BPF tracers and tracing in general comes to mind here... > my concern is that tracing is suitable for dynamic debugging, but these context info are mostly static. Perhaps I am missing some tracing features. Thanks, Jacob > > Joerg > [Jacob Pan]