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Groups > linux.kernel > #1642854
| From | Boris Ostrovsky <boris.ostrovsky@oracle.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 08/18] xen/pvcalls: implement connect command |
| Date | 2017-05-17 00:00 +0200 |
| Message-ID | <tHSFA-2Gq-7@gated-at.bofh.it> (permalink) |
| References | <tHuWC-4t8-7@gated-at.bofh.it> <tHuWC-4t8-9@gated-at.bofh.it> <tHuWD-4t8-49@gated-at.bofh.it> <tHAIF-89Z-1@gated-at.bofh.it> <tHRTb-2nV-7@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
>>> + ret = xenbus_map_ring_valloc(dev, &req->u.connect.ref, 1, &page);
>>> + if (ret < 0) {
>>> + sock_release(map->sock);
>>> + kfree(map);
>>> + goto out;
>>> + }
>>> + map->ring = page;
>>> + map->ring_order = map->ring->ring_order;
>>> + /* first read the order, then map the data ring */
>>> + virt_rmb();
>>
>> Not sure I understand what the barrier is for here. I don't think compiler
>> will reorder ring_order access with the call.
> It's to avoid using the live version of ring_order to map the data ring
> pages (the other end could be changing that value at any time). We want
> to be sure that the compiler doesn't optimize out map->ring_order and
> use map->ring->ring_order instead.
Wouldn't WRITE_ONCE(map->ring_order, map->ring->ring_order) be the right
primitive then?
And also: if the other side changes ring size, what are we mapping then?
It's obsolete by now.
-boris
>
>
>>> + if (map->ring_order > MAX_RING_ORDER) {
>>> + ret = -EFAULT;
>>> + goto out;
>>> + }
>> If the barrier is indeed needed this check belongs before it.
> I don't think so, see above.
>
>
>>
>>> + ret = xenbus_map_ring_valloc(dev, map->ring->ref,
>>> + (1 << map->ring_order), &page);
>>> + if (ret < 0) {
>>> + sock_release(map->sock);
>>> + xenbus_unmap_ring_vfree(dev, map->ring);
>>> + kfree(map);
>>> + goto out;
>>> + }
>>> + map->bytes = page;
>>>
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[PATCH 01/18] xen: introduce the pvcalls interface header Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 14/18] xen/pvcalls: disconnect and module_exit Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 02/18] xen/pvcalls: introduce the pvcalls xenbus backend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 15/18] xen/pvcalls: introduce the ioworker Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 09/18] xen/pvcalls: implement bind command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
Re: [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-05-16 03:50 +0200
Re: [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-16 22:10 +0200
Re: [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-16 22:30 +0200
Re: [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend Juergen Gross <jgross@suse.com> - 2017-05-16 08:50 +0200
Re: [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-16 22:00 +0200
Re: [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend Juergen Gross <jgross@suse.com> - 2017-05-17 07:30 +0200
Re: [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-18 23:20 +0200
Re: [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-20 00:40 +0200
[PATCH 10/18] xen/pvcalls: implement listen command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 13/18] xen/pvcalls: implement release command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 06/18] xen/pvcalls: handle commands from the frontend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
Re: [PATCH 06/18] xen/pvcalls: handle commands from the frontend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-05-16 04:20 +0200
Re: [PATCH 06/18] xen/pvcalls: handle commands from the frontend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-16 23:00 +0200
[PATCH 07/18] xen/pvcalls: implement socket command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
Re: [PATCH 07/18] xen/pvcalls: implement socket command Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-05-16 04:30 +0200
Re: [PATCH 07/18] xen/pvcalls: implement socket command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-16 22:50 +0200
[PATCH 12/18] xen/pvcalls: implement poll command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 16/18] xen/pvcalls: implement read Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 08/18] xen/pvcalls: implement connect command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
Re: [PATCH 08/18] xen/pvcalls: implement connect command Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-05-16 04:50 +0200
Re: [PATCH 08/18] xen/pvcalls: implement connect command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-16 23:10 +0200
Re: [PATCH 08/18] xen/pvcalls: implement connect command Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-05-17 00:00 +0200
Re: [PATCH 08/18] xen/pvcalls: implement connect command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-18 21:20 +0200
Re: [PATCH 08/18] xen/pvcalls: implement connect command Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-05-18 22:30 +0200
[PATCH 11/18] xen/pvcalls: implement accept command Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:40 +0200
[PATCH 05/18] xen/pvcalls: connect to a frontend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:50 +0200
Re: [PATCH 05/18] xen/pvcalls: connect to a frontend Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-05-16 04:10 +0200
Re: [PATCH 05/18] xen/pvcalls: connect to a frontend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-16 22:30 +0200
Re: [PATCH 05/18] xen/pvcalls: connect to a frontend Stefano Stabellini <sstabellini@kernel.org> - 2017-05-16 22:40 +0200
[PATCH 04/18] xen/pvcalls: xenbus state handling Stefano Stabellini <sstabellini@kernel.org> - 2017-05-15 22:50 +0200
Re: [PATCH 04/18] xen/pvcalls: xenbus state handling Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-05-16 03:50 +0200
Re: [PATCH 04/18] xen/pvcalls: xenbus state handling Stefano Stabellini <sstabellini@kernel.org> - 2017-05-16 22:20 +0200
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