From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: Re: [PATCH 1/4] expand x86 arch_shared_info to support linear p2m list Date: Fri, 14 Nov 2014 13:53:08 +0100 Message-ID: <5465FB34.9010606@suse.com> References: <1415957846-22703-1-git-send-email-jgross@suse.com> <1415957846-22703-2-git-send-email-jgross@suse.com> <5465EA63.3010007@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5465EA63.3010007@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper , xen-devel@lists.xensource.com, jbeulich@suse.com, konrad.wilk@oracle.com, david.vrabel@citrix.com List-Id: xen-devel@lists.xenproject.org On 11/14/2014 12:41 PM, Andrew Cooper wrote: > On 14/11/14 09:37, Juergen Gross wrote: >> The x86 struct arch_shared_info field pfn_to_mfn_frame_list_list >> currently contains the mfn of the top level page frame of the 3 level >> p2m tree, which is used by the Xen tools during saving and restoring >> (and live migration) of pv domains and for crash dump analysis. With >> three levels of the p2m tree it is possible to support up to 512 GB of >> RAM for a 64 bit pv domain. >> >> A 32 bit pv domain can support more, as each memory page can hold 1024 >> instead of 512 entries, leading to a limit of 4 TB. >> >> To be able to support more RAM on x86-64 switch to a virtual mapped >> p2m list. >> >> This patch expands struct arch_shared_info with a new p2m list virtual >> address and the mfn of the page table root. The new information is >> indicated by the domain to be valid by storing ~0UL into >> pfn_to_mfn_frame_list_list. The hypervisor indicates usability of this >> feature by a new flag XENFEAT_virtual_p2m. > > How do you envisage this being used? Are you expecting the tools to do > manual pagetable walks using xc_map_foreign_xxx() ? Yes. Not very different compared to today's mapping via the 3 level p2m tree. Just another entry format, 4 instead of 3 levels and starting at an offset. Juergen