From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hongkaixing Subject: Re: [PATCH 1 of 2] x86/mm: Allow a page in p2m_ram_paged_out state to be loaded Date: Wed, 11 Jan 2012 15:45:17 +0800 Message-ID: <000a01ccd034$f7037ee0$e50a7ca0$@com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-reply-to: Content-language: zh-cn List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: 'Andres Lagar-Cavilla' , xen-devel@lists.xensource.com Cc: xiaowei.yang@huawei.com, olaf@aepfle.de, andres@gridcentric.ca, yanqiangjun@huawei.com, tim@xen.org, bicky.shi@huawei.com, adin@gridcentric.ca List-Id: xen-devel@lists.xenproject.org I think it may have many unpredicted risks. After p2mt is changed to p2m_ram_rw, Domain guest can access this page unrestrictedly without being trapped in xen. But at this time, the page is not prepared. > -----Original Message----- > From: xen-devel-bounces@lists.xensource.com [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Andres Lagar-Cavilla > Sent: Tuesday, January 10, 2012 5:41 AM > To: xen-devel@lists.xensource.com > Cc: andres@gridcentric.ca; tim@xen.org; olaf@aepfle.de; adin@gridcentric.ca > Subject: [Xen-devel] [PATCH 1 of 2] x86/mm: Allow a page in p2m_ram_paged_out state to be loaded > > xen/arch/x86/mm/p2m.c | 15 +++++++++++---- > 1 files changed, 11 insertions(+), 4 deletions(-) > > > This removes the need for a page to be accessed in order to be pageable > again. A pager can now page-in pages at will with no need to map them > in a separate thread. > > Signed-off-by: Andres Lagar-Cavilla > Acked-by: Tim Deegan > > diff -r 90f764bf02c3 -r f7c330d5b4b5 xen/arch/x86/mm/p2m.c > --- a/xen/arch/x86/mm/p2m.c > +++ b/xen/arch/x86/mm/p2m.c > @@ -964,7 +964,7 @@ void p2m_mem_paging_populate(struct doma > int p2m_mem_paging_prep(struct domain *d, unsigned long gfn, uint64_t buffer) > { > struct page_info *page; > - p2m_type_t p2mt; > + p2m_type_t p2mt, target_p2mt; > p2m_access_t a; > mfn_t mfn; > struct p2m_domain *p2m = p2m_get_hostp2m(d); > @@ -982,8 +982,8 @@ int p2m_mem_paging_prep(struct domain *d > mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, p2m_query, NULL); > > ret = -ENOENT; > - /* Allow only missing pages */ > - if ( p2mt != p2m_ram_paging_in_start ) > + /* Allow missing pages */ > + if ( (p2mt != p2m_ram_paging_in_start) && (p2mt != p2m_ram_paged) ) > goto out; > > /* Allocate a page if the gfn does not have one yet */ > @@ -1018,8 +1018,15 @@ int p2m_mem_paging_prep(struct domain *d > } > } > > + target_p2mt = (p2mt == p2m_ram_paging_in_start) ? > + /* If we kicked the pager with a populate event, the pager will send > + * a resume event back */ > + p2m_ram_paging_in : > + /* If this was called asynchronously by the pager, then we can > + * transition directly to the final guest-accessible type */ > + (paging_mode_log_dirty(d) ? p2m_ram_logdirty : p2m_ram_rw); > /* Fix p2m mapping */ > - set_p2m_entry(p2m, gfn, mfn, PAGE_ORDER_4K, p2m_ram_paging_in, a); > + set_p2m_entry(p2m, gfn, mfn, PAGE_ORDER_4K, target_p2mt, a); > > atomic_dec(&d->paged_pages); > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel