From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Deegan Subject: Re: where is writable page table implemented? Date: Tue, 1 Apr 2008 16:17:53 +0000 Message-ID: <20080401161753.GD4628@york.uk.xensource.com> References: <20080324162510.GD30315@york.uk.xensource.com> <20080325104351.GA30991@york.uk.xensource.com> <20080401083825.GA4628@york.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: weiming Cc: xen-devel List-Id: xen-devel@lists.xenproject.org At 11:37 -0400 on 01 Apr (1207049874), weiming wrote: > Do you know under which situation we use writable page table instead of > calling update_va_mapping? Not in any detail. > And do you know the purpose of the counter defined in > page_info.u.in_use.type_info? > I understand that xen needs to keep track of the type of each page > (L1_page_table_page, L2_page_table_page, pinned, unpinned, validated, etc), > but why do we need to use the lower 26 bits of "type_info" as a counter? (in > "get_page_type()", the counter is increased. ) Similarly, get_page() / > put_page() also increases/decreases the page.count_info. Could you please > give me some hint about the usage of such counters? You should read the comments at the top of xen/arch/x86/mm.c. Tim. -- Tim Deegan Principal Software Engineer, Citrix Systems (R&D) Ltd. [Company #02300071, SL9 0DZ, UK.]