Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751245AbdFAPRH (ORCPT ); Thu, 1 Jun 2017 11:17:07 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:48401 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751058AbdFAPRG (ORCPT ); Thu, 1 Jun 2017 11:17:06 -0400 Subject: Re: [PATCH] xen/privcmd: Support correctly 64KB page granularity when mapping memory To: Julien Grall , xen-devel@lists.xen.org References: <20170531130357.14492-1-julien.grall@arm.com> <7199e366-f56a-acc8-ffa5-0c85d6975049@oracle.com> <592886a8-1443-6475-e318-85cb9acecead@arm.com> <0b91491d-8f67-fa22-8b27-7692f00bba51@arm.com> Cc: sstabellini@kernel.org, jgross@suse.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Feng Kan From: Boris Ostrovsky Message-ID: Date: Thu, 1 Jun 2017 11:16:46 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <0b91491d-8f67-fa22-8b27-7692f00bba51@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2472 Lines: 71 On 06/01/2017 10:01 AM, Julien Grall wrote: > Hi Boris, > > On 01/06/17 14:33, Boris Ostrovsky wrote: >> On 06/01/2017 08:50 AM, Julien Grall wrote: >>> Hi Boris, >>> >>> On 31/05/17 14:54, Boris Ostrovsky wrote: >>>> On 05/31/2017 09:03 AM, Julien Grall wrote: >>>>> Commit 5995a68 "xen/privcmd: Add support for Linux 64KB page >>>>> granularity" did >>>>> not go far enough to support 64KB in mmap_batch_fn. >>>>> >>>>> The variable 'nr' is the number of 4KB chunk to map. However, when >>>>> Linux >>>>> is using 64KB page granularity the array of pages >>>>> (vma->vm_private_data) >>>>> contain one page per 64KB. Fix it by incrementing st->index >>>>> correctly. >>>>> >>>>> Furthermore, st->va is not correctly incremented as PAGE_SIZE != >>>>> XEN_PAGE_SIZE. >>>>> >>>>> Fixes: 5995a68 ("xen/privcmd: Add support for Linux 64KB page >>>>> granularity") >>>>> CC: stable@vger.kernel.org >>>>> Reported-by: Feng Kan >>>>> Signed-off-by: Julien Grall >>>>> --- >>>>> drivers/xen/privcmd.c | 4 ++-- >>>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c >>>>> index 7a92a5e1d40c..feca75b07fdd 100644 >>>>> --- a/drivers/xen/privcmd.c >>>>> +++ b/drivers/xen/privcmd.c >>>>> @@ -362,8 +362,8 @@ static int mmap_batch_fn(void *data, int nr, >>>>> void *state) >>>>> st->global_error = 1; >>>>> } >>>>> } >>>>> - st->va += PAGE_SIZE * nr; >>>>> - st->index += nr; >>>>> + st->va += XEN_PAGE_SIZE * nr; >>>>> + st->index += nr / XEN_PFN_PER_PAGE; >>>>> >>>>> return 0; >>>>> } >>>> >>>> >>>> Are we still using PAGE_MASK for xen_remap_domain_gfn_array()? >>> >>> Do you mean in the xen_xlate_remap_gfn_array implementation? If so >>> there are no use of PAGE_MASK as the code has been converted to >>> support 64K page granularity. >>> >>> If you mean the x86 version of xen_remap_domain_gfn_array, then we >>> don't really care as x86 only use 4KB page granularity. >> >> >> I meant right above the change that you made. Should it also be replaced >> with XEN_PAGE_MASK? (Sorry for being unclear.) > > Oh. The code in xen_remap_domain_gfn_array is relying on st->va to be > page aligned. So I think we want to keep PAGE_MASK here. Doe this imply then that 'nr' 4K pages is integral number of PAGE_SIZE (i.e. (nr*XEN_PAGE_SIZE) % PAGE_SIZE == 0) and if yes --- do we test this somewhere? I don't see it. -boris