From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mukesh Rathor Subject: Re: [RFC PATCH] PVH: cleanup of p2m upon p2m destroy Date: Fri, 31 Jan 2014 18:38:38 -0800 Message-ID: <20140131183838.27075db3@mantra.us.oracle.com> References: <20131216174728.2ba3ad9a@mantra.us.oracle.com> <52B01C88020000780010E042@nat28.tlf.novell.com> <20131217101957.GB32721@deinos.phlegethon.org> <20131217184412.2372eb45@mantra.us.oracle.com> <20131218100958.GB24792@deinos.phlegethon.org> <20131218165152.GO24792@deinos.phlegethon.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1W9QTm-0001uo-Pp for xen-devel@lists.xenproject.org; Sat, 01 Feb 2014 02:38:47 +0000 In-Reply-To: <20131218165152.GO24792@deinos.phlegethon.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Tim Deegan Cc: xen-devel , Jan Beulich List-Id: xen-devel@lists.xenproject.org On Wed, 18 Dec 2013 17:51:52 +0100 Tim Deegan wrote: > At 11:09 +0100 on 18 Dec (1387361398), Tim Deegan wrote: > > > An alternative might be to just create a link list then and walk > > > it. In general, foreign mappings should be very small, so the > > > overhead of 16 bytes per page for the link list might not be too > > > bad. I will code it if there is no disagreement from any > > > maintainer... everyone has different ideas :)... > > > > I think it would be best to walk the p2m trie (i.e. bounded by > > amount of RAM, rather than max GFN) and do it preemptably. I'll > > look into something like that for the mem_sharing loop today, and > > foreign mapping code can reuse it. > > What I've ended up with is making p2m_change_entry_type_global() > preemptible (which is a bigger task but will be needed as domains get > bigger). Do you think that using that function to switch all mappings > from p2m_foreign to p2m_invalid, appropriately late in the teardown, > will be good enough for what you need? > > Cheers, > > Tim. Finally, coming back to this, the answer is yes. Looks like all I need to do is: diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c index 9faa663..268a8a2 100644 --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -470,6 +470,10 @@ void p2m_teardown(struct p2m_domain *p2m) p2m_lock(p2m); + /* pvh: we must release refcnt on all foreign pages */ + if ( is_pvh_domain(d) ) + p2m_change_entry_type_global(d, p2m_map_foreign, p2m_invalid); + /* Try to unshare any remaining shared p2m entries. Safeguard * Since relinquish_shared_pages should have done the work. */ for ( gfn=0; gfn < p2m->max_mapped_pfn; gfn++ ) In this call, the new atomic_write_ept_entry() will DTRT: static inline void atomic_write_ept_entry(ept_entry_t *entryptr, const ept_entry_t *new) { if ( p2m_is_foreign(new->sa_p2mt) ) { struct page_info *page; struct domain *fdom; ASSERT(mfn_valid(new->mfn)); page = mfn_to_page(new->mfn); fdom = page_get_owner(page); get_page(page, fdom); } if ( p2m_is_foreign(entryptr->sa_p2mt) ) put_page(mfn_to_page(entryptr->mfn)); write_atomic(&entryptr->epte, new->epte); } If that sounds ok, I'm ready to submit dom0 PVH patches. Pl lmk. thanks Mukesh