From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [Xen-devel] [PATCH 08/11] xen p2m: transparently change the p2m mappings in the m2p override Date: Wed, 15 Dec 2010 15:36:34 -0800 Message-ID: <4D095102.6010505@goop.org> References: <1292420446-3348-8-git-send-email-stefano.stabellini@eu.citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1292420446-3348-8-git-send-email-stefano.stabellini@eu.citrix.com> Sender: linux-kernel-owner@vger.kernel.org To: stefano.stabellini@eu.citrix.com Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, Jeremy Fitzhardinge , Konrad Rzeszutek Wilk List-Id: xen-devel@lists.xenproject.org On 12/15/2010 05:40 AM, stefano.stabellini@eu.citrix.com wrote: > From: Stefano Stabellini > > In m2p_add_override store the original mfn into page->index and then > change the p2m mapping, setting mfns as FOREIGN_FRAME. > > In m2p_remove_override restore the original mapping. > > Signed-off-by: Stefano Stabellini > --- > arch/x86/xen/p2m.c | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c > index 8db19d5..7dde8e4 100644 > --- a/arch/x86/xen/p2m.c > +++ b/arch/x86/xen/p2m.c > @@ -407,8 +407,11 @@ static unsigned long mfn_hash(unsigned long mfn) > void m2p_add_override(unsigned long mfn, struct page *page) > { > unsigned long flags; > + unsigned long pfn = page_to_pfn(page); > page->private = mfn; > + page->index = pfn_to_mfn(pfn); Is there any risk that a page being used for a granted mfn will end up getting xen_create_contiguous_region() applied to it via the DMA API? That would be messy... J > > + __set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)); > spin_lock_irqsave(&m2p_override_lock, flags); > list_add(&page->lru, &m2p_overrides[mfn_hash(mfn)]); > spin_unlock_irqrestore(&m2p_override_lock, flags); > @@ -420,6 +423,7 @@ void m2p_remove_override(struct page *page) > spin_lock_irqsave(&m2p_override_lock, flags); > list_del(&page->lru); > spin_unlock_irqrestore(&m2p_override_lock, flags); > + __set_phys_to_machine(page_to_pfn(page), page->index); > } > > struct page *m2p_find_override(unsigned long mfn)