Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751309AbdFAUlx (ORCPT ); Thu, 1 Jun 2017 16:41:53 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:31099 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751125AbdFAUlw (ORCPT ); Thu, 1 Jun 2017 16:41:52 -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> <1f38dcc0-8538-b8e5-a792-85867ea1c44d@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: <0e7b0066-6219-79f8-5b17-b997a400d3f6@oracle.com> Date: Thu, 1 Jun 2017 16:41:21 -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: <1f38dcc0-8538-b8e5-a792-85867ea1c44d@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3259 Lines: 96 On 06/01/2017 11:38 AM, Julien Grall wrote: > Hi Boris, > > On 01/06/17 16:16, Boris Ostrovsky wrote: >> 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. > I now see that this should (obviously) stay as PAGE_MASK, so Reviewed-by: Boris Ostrovsky but > nr might be smaller for the last batch. But all the intermediate batch > should have ((nr * XEN_PAGE_SIZE) % PAGE_SIZE == 0). how can we have nr not covering full PAGE_SIZEs? If you are using 64K pages, how can you map, say, only 4K (if nr==1)? -boris > > I think the BUILD_BUG_ON in privcmd_ioctl_mmap_batch ensure that all > the intermediate batch will always be an integral number of PAGE_SIZE. > > Cheers, >