Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754467Ab0KKQkv (ORCPT ); Thu, 11 Nov 2010 11:40:51 -0500 Received: from rcsinet10.oracle.com ([148.87.113.121]:22488 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754061Ab0KKQku (ORCPT >); Thu, 11 Nov 2010 11:40:50 -0500 Date: Thu, 11 Nov 2010 11:40:29 -0500 From: Konrad Rzeszutek Wilk To: Stefano Stabellini Cc: Jeremy Fitzhardinge , Ian Campbell , xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org Subject: Re: [Xen-devel] [PATCH] xen: set vma flag VM_PFNMAP in the privcmd mmap file_op Message-ID: <20101111164029.GB29405@dumpdata.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2628 Lines: 72 On Thu, Nov 11, 2010 at 03:55:49PM +0000, Stefano Stabellini wrote: > Hi all, > this patch fixes the dom0 kernel crash when creating a VM. > Now I am able to create VMs successfully on 2.6.37 rc1, even though > without disk or network access. > > --- > > xen: set vma flag VM_PFNMAP in the privcmd mmap file_op > > Set VM_PFNMAP in the privcmd mmap file_op, rather than later in > xen_remap_domain_mfn_range when it is too late because > vma_wants_writenotify has already been called and vm_page_prot has So vma_wants_writenotify sets the invalid flags on vma->vm_flags? > already been modified. By whom? vma_wants_writenotify looks to just return 0 or 1 Ah, depending on that return value it sets vma->vm_page_prot. That looks odd, so if this: 1215 if (vma_wants_writenotify(vma)) 1216 vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED); 1217 does not set the vma->vm_page_prot we never set the vm_page_prot? .. and it looks to not set that value earlier on either. So VM_PFNMAP inhibits the mmap code from setting the vm_page_prot. Is that what we want, not have vma->vm_page_prot set anything? Why? > > Signed-off-by: Stefano Stabellini > > diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c > index c237b81..2be1f36 100644 > --- a/arch/x86/xen/mmu.c > +++ b/arch/x86/xen/mmu.c > @@ -2627,7 +2627,7 @@ int xen_remap_domain_mfn_range(struct vm_area_struct *vma, > > prot = __pgprot(pgprot_val(prot) | _PAGE_IOMAP); > > - vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP; > + BUG_ON(!(vma->vm_flags & (VM_PFNMAP | VM_RESERVED | VM_IO))); > > rmd.mfn = mfn; > rmd.prot = prot; > diff --git a/drivers/xen/xenfs/privcmd.c b/drivers/xen/xenfs/privcmd.c > index f80be7f..9aab216 100644 > --- a/drivers/xen/xenfs/privcmd.c > +++ b/drivers/xen/xenfs/privcmd.c > @@ -385,7 +385,7 @@ static int privcmd_mmap(struct file *file, struct vm_area_struct *vma) > return -ENOSYS; > > /* DONTCOPY is essential for Xen as copy_page_range is broken. */ > - vma->vm_flags |= VM_RESERVED | VM_IO | VM_DONTCOPY; > + vma->vm_flags |= VM_RESERVED | VM_IO | VM_DONTCOPY | VM_PFNMAP; > vma->vm_ops = &privcmd_vm_ops; > vma->vm_private_data = NULL; > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/