From mboxrd@z Thu Jan 1 00:00:00 1970 From: Muli Ben-Yehuda Subject: Re: [PATCH] Handle vma regions with no backing page (v2) Date: Wed, 30 Apr 2008 09:11:40 +0300 Message-ID: <20080430061140.GE7378@il.ibm.com> References: <1209496160-20482-1-git-send-email-aliguori@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, Andrea Arcangeli , Ben-Ami Yassour1 , Avi Kivity To: Anthony Liguori Return-path: Content-Disposition: inline In-Reply-To: <1209496160-20482-1-git-send-email-aliguori@us.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org On Tue, Apr 29, 2008 at 02:09:20PM -0500, Anthony Liguori wrote: > This patch allows VMA's that contain no backing page to be used for guest > memory. This is a drop-in replacement for Ben-Ami's first page in his direct > mmio series. Here, we continue to allow mmio pages to be represented in the > rmap. > > Since v1, I've taken into account Andrea's suggestions at using VM_PFNMAP > instead of VM_IO and changed the BUG_ON to a return of bad_page. > > Signed-off-by: Anthony Liguori > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 1d7991a..64e5efe 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -532,6 +532,7 @@ pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn) > struct page *page[1]; > unsigned long addr; > int npages; > + pfn_t pfn; > > might_sleep(); > > @@ -544,19 +545,35 @@ pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn) > npages = get_user_pages(current, current->mm, addr, 1, 1, 1, page, > NULL); > > - if (npages != 1) { > - get_page(bad_page); > - return page_to_pfn(bad_page); > - } > + if (unlikely(npages != 1)) { > + struct vm_area_struct *vma; > > - return page_to_pfn(page[0]); > + vma = find_vma(current->mm, addr); > + if (vma == NULL || addr >= vma->vm_start || > + !(vma->vm_flags & VM_PFNMAP)) { Isn't the check for addr backwards here? For the VMA we would like to to find, vma->vm_start <= addr < vma->vm_end. Cheers, Muli ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone