From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] [PATCH V2 3/3] xen: eliminate scalability issues from initial mapping setup Date: Wed, 17 Sep 2014 15:42:47 +0100 Message-ID: <54199DE7.6010306@citrix.com> References: <1410927157-15069-1-git-send-email-jgross@suse.com> <1410927157-15069-4-git-send-email-jgross@suse.com> <54199589.9040703@citrix.com> <541998CB.4000409@suse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <541998CB.4000409@suse.com> Sender: linux-kernel-owner@vger.kernel.org To: Juergen Gross , linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, jbeulich@suse.com List-Id: xen-devel@lists.xenproject.org On 17/09/14 15:20, Juergen Gross wrote: > On 09/17/2014 04:07 PM, David Vrabel wrote: >> >> >> Are you missing a ClearPagePinned(..) here? > > Probably, yes. Jan pointed out that this is not needed. >>> @@ -1529,6 +1604,22 @@ static pte_t __init mask_rw_pte(pte_t *ptep, >>> pte_t pte) >>> #else /* CONFIG_X86_64 */ >>> static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte) >>> { >>> + unsigned long pfn; >>> + >>> + if (xen_feature(XENFEAT_writable_page_tables) || >>> + xen_feature(XENFEAT_auto_translated_physmap) || >>> + xen_start_info->mfn_list >= __START_KERNEL_map) >>> + return pte; >>> + >>> + /* >>> + * Pages belonging to the initial p2m list mapped outside the >>> default >>> + * address range must be mapped read-only. >> >> Why? I didn't think was anything special about these MFNs. > > The hypervisor complained when I did otherwise. I think the main reason > is that the hypervisor will set up some more page tables to be able to > map then mfn_list outside the "normal" address range. They are located > in the range starting at xen_start_info->first_p2m_pfn (otherwise the > info in first_p2m_pfn and nr_p2m_frames wouldn't be needed). Ok. Can you expand the comment to say this? David