From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Yu, Zhang" Subject: Re: [PATCH 3/3] tools: introduce parameter max_ranges. Date: Wed, 20 Jan 2016 11:33:28 +0800 Message-ID: <569F0008.1010201@linux.intel.com> References: <1453195678-25944-1-git-send-email-yu.c.zhang@linux.intel.com> <1453195678-25944-4-git-send-email-yu.c.zhang@linux.intel.com> <20160119115349.GV1691@citrix.com> <7a1e981ca15b491e878fb32287f5ea7a@AMSPEX02CL03.citrite.net> <20160119143725.GI1691@citrix.com> <968fc8fc8f824ee7903fe7c8cbb7b5c0@AMSPEX02CL03.citrite.net> <20160119150400.GK1691@citrix.com> <1453216725.29930.84.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: "Tian, Kevin" , Ian Campbell , Wei Liu , Paul Durrant Cc: "Keir (Xen.org)" , Andrew Cooper , "xen-devel@lists.xen.org" , Stefano Stabellini , "Lv, Zhiyuan" , "jbeulich@suse.com" List-Id: xen-devel@lists.xenproject.org On 1/20/2016 11:14 AM, Tian, Kevin wrote: >> From: Ian Campbell [mailto:ian.campbell@citrix.com] >> Sent: Tuesday, January 19, 2016 11:19 PM >> >> On Tue, 2016-01-19 at 15:04 +0000, Wei Liu wrote: >> >> This patch doesn't seem to have been CCd to the tools maintainers, adding >> Ian too, I think everyone else was picked up along the way. >> >> Please use ./scripts/get_maintainers.pl in the future. >> >>> On Tue, Jan 19, 2016 at 02:47:40PM +0000, Paul Durrant wrote: >>> [...] >>>>> ranges so perhaps the parameter name could be >>>>> 'max_wp_memory_ranges'? >>>>>> >>>>> >>>>> What does "WP" mean? "Write Protected"? >>>>> >>>> >>>> Yes. >>>> >>>>> Is this parameter closely related to IOREQ server? Should it contain >>>>> "ioreq" somehow? >>>>> >>>> >>>> It is closely related but ioreq server is an implementation detail so >>>> do we want to expose it as a tunable? The concept we need to capture >>>> is that the toolstack can tune the limit of the maximum number of >>>> pages in the VM that can be set such that writes are emulated (but >>>> reads are as for normal ram). Or I guess we could get very specific >>>> and call it something like 'max_gtt_shadows'? >>> >>> I would prefer generic concept in this case ("wp"). Let's wait a bit for >>> other people to voice their opinion. >>> >>> Whichever one we pick it the meaning of the acronym needs to be clearly >>> documented... >> >> I've got no ideas for a better name, "max_ranges" is clearly too generic >> though. >> >> One thought -- does XenGT require some other configuration option to enable >> it or maybe a privilege which the target domain must necessarily have? >> Could we use something like one of those to cause the t/stack to just DTRT >> without the user having to micromanage the amount of pages which are >> allowed to have this property? >> > > Using "wp" is clear to me. > Thank you all. :) So how about "max_wp_ram_ranges"? And the "wp" shall be well explained in documentation. > As a feature this write-protection has nothing to be GPU virtualization specific. > In the future the same mediated pass-through idea used in XenGT may be > used on other I/O devices which need to shadow some structure w/ requirement > to write-protect guest memory. So it's not good to tie this to either XenGT > or GTT. > Thank you, Kevin. Well, if this parameter is not supposed to be xengt specific, we do not need to connect it with any xengt flag such as ."vgt=1" or "GVT-g=1". Hence the user will have to configure the max_wp_ram_ranges himself, right? B.R. Yu > Thanks > Kevin >