Messages in this thread | | | Subject | Re: [PATCH] xen/privcmd: Support correctly 64KB page granularity when mapping memory | From | Julien Grall <> | Date | Tue, 6 Jun 2017 17:17:54 +0100 |
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Hi,
It has been reviewed-by Boris but I don't see the patch queued. Would it be possible to queue it for 4.12?
Cheers,
On 01/06/17 21:41, Boris Ostrovsky wrote: > 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 <fkan@apm.com> >>>>>>>> Signed-off-by: Julien Grall <julien.grall@arm.com> >>>>>>>> --- >>>>>>>> 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 <boris.ostrovsky@oracle.com> > > 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, >> >
-- Julien Grall
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