https://github.com/torvalds/linux
Revision c5c9f25b98a568451d665afe4aeefe17bf9f2995 authored by Nishanth Aravamudan on 24 November 2015, 16:55:05 UTC, committed by Jens Axboe on 24 November 2015, 22:05:51 UTC
We received a bug report recently when DDW (64-bit direct DMA on Power) is not enabled for NVMe devices. In that case, we fall back to 32-bit DMA via the IOMMU, which is always done via 4K TCEs (Translation Control Entries). The NVMe device driver, though, assumes that the DMA alignment for the PRP entries will match the device's page size, and that the DMA aligment matches the kernel's page aligment. On Power, the the IOMMU page size, as mentioned above, can be 4K, while the device can have a page size of 8K, while the kernel has a page size of 64K. This eventually trips the BUG_ON in nvme_setup_prps(), as we have a 'dma_len' that is a multiple of 4K but not 8K (e.g., 0xF000). In this particular case of page sizes, we clearly want to use the IOMMU's page size in the driver. And generally, the NVMe driver in this function should be using the IOMMU's page size for the default device page size, rather than the kernel's page size. There is not currently an API to obtain the IOMMU's page size across all architectures and in the interest of a stop-gap fix to this functional issue, default the NVMe device page size to 4K, with the intent of adding such an API and implementation across all architectures in the next merge window. With the functionally equivalent v3 of this patch, our hardware test exerciser survives when using 32-bit DMA; without the patch, the kernel will BUG within a few minutes. Signed-off-by: Nishanth Aravamudan <nacc at linux.vnet.ibm.com> Signed-off-by: Jens Axboe <axboe@fb.com>
1 parent 6ffeba9
Tip revision: c5c9f25b98a568451d665afe4aeefe17bf9f2995 authored by Nishanth Aravamudan on 24 November 2015, 16:55:05 UTC
NVMe: default to 4k device page size
NVMe: default to 4k device page size
Tip revision: c5c9f25
stable_kernel_rules.txt
Everything you ever wanted to know about Linux -stable releases.
Rules on what kind of patches are accepted, and which ones are not, into the
"-stable" tree:
- It must be obviously correct and tested.
- It cannot be bigger than 100 lines, with context.
- It must fix only one thing.
- It must fix a real bug that bothers people (not a, "This could be a
problem..." type thing).
- It must fix a problem that causes a build error (but not for things
marked CONFIG_BROKEN), an oops, a hang, data corruption, a real
security issue, or some "oh, that's not good" issue. In short, something
critical.
- Serious issues as reported by a user of a distribution kernel may also
be considered if they fix a notable performance or interactivity issue.
As these fixes are not as obvious and have a higher risk of a subtle
regression they should only be submitted by a distribution kernel
maintainer and include an addendum linking to a bugzilla entry if it
exists and additional information on the user-visible impact.
- New device IDs and quirks are also accepted.
- No "theoretical race condition" issues, unless an explanation of how the
race can be exploited is also provided.
- It cannot contain any "trivial" fixes in it (spelling changes,
whitespace cleanups, etc).
- It must follow the Documentation/SubmittingPatches rules.
- It or an equivalent fix must already exist in Linus' tree (upstream).
Procedure for submitting patches to the -stable tree:
- If the patch covers files in net/ or drivers/net please follow netdev stable
submission guidelines as described in
Documentation/networking/netdev-FAQ.txt
- Security patches should not be handled (solely) by the -stable review
process but should follow the procedures in Documentation/SecurityBugs.
For all other submissions, choose one of the following procedures:
--- Option 1 ---
To have the patch automatically included in the stable tree, add the tag
Cc: stable@vger.kernel.org
in the sign-off area. Once the patch is merged it will be applied to
the stable tree without anything else needing to be done by the author
or subsystem maintainer.
--- Option 2 ---
After the patch has been merged to Linus' tree, send an email to
stable@vger.kernel.org containing the subject of the patch, the commit ID,
why you think it should be applied, and what kernel version you wish it to
be applied to.
--- Option 3 ---
Send the patch, after verifying that it follows the above rules, to
stable@vger.kernel.org. You must note the upstream commit ID in the
changelog of your submission, as well as the kernel version you wish
it to be applied to.
Option 1 is *strongly* preferred, is the easiest and most common. Options 2 and
3 are more useful if the patch isn't deemed worthy at the time it is applied to
a public git tree (for instance, because it deserves more regression testing
first). Option 3 is especially useful if the patch needs some special handling
to apply to an older kernel (e.g., if API's have changed in the meantime).
Note that for Option 3, if the patch deviates from the original upstream patch
(for example because it had to be backported) this must be very clearly
documented and justified in the patch description.
The upstream commit ID must be specified with a separate line above the commit
text, like this:
commit <sha1> upstream.
Additionally, some patches submitted via Option 1 may have additional patch
prerequisites which can be cherry-picked. This can be specified in the following
format in the sign-off area:
Cc: <stable@vger.kernel.org> # 3.3.x: a1f84a3: sched: Check for idle
Cc: <stable@vger.kernel.org> # 3.3.x: 1b9508f: sched: Rate-limit newidle
Cc: <stable@vger.kernel.org> # 3.3.x: fd21073: sched: Fix affinity logic
Cc: <stable@vger.kernel.org> # 3.3.x
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The tag sequence has the meaning of:
git cherry-pick a1f84a3
git cherry-pick 1b9508f
git cherry-pick fd21073
git cherry-pick <this commit>
Also, some patches may have kernel version prerequisites. This can be
specified in the following format in the sign-off area:
Cc: <stable@vger.kernel.org> # 3.3.x-
The tag has the meaning of:
git cherry-pick <this commit>
For each "-stable" tree starting with the specified version.
Following the submission:
- The sender will receive an ACK when the patch has been accepted into the
queue, or a NAK if the patch is rejected. This response might take a few
days, according to the developer's schedules.
- If accepted, the patch will be added to the -stable queue, for review by
other developers and by the relevant subsystem maintainer.
Review cycle:
- When the -stable maintainers decide for a review cycle, the patches will be
sent to the review committee, and the maintainer of the affected area of
the patch (unless the submitter is the maintainer of the area) and CC: to
the linux-kernel mailing list.
- The review committee has 48 hours in which to ACK or NAK the patch.
- If the patch is rejected by a member of the committee, or linux-kernel
members object to the patch, bringing up issues that the maintainers and
members did not realize, the patch will be dropped from the queue.
- At the end of the review cycle, the ACKed patches will be added to the
latest -stable release, and a new -stable release will happen.
- Security patches will be accepted into the -stable tree directly from the
security kernel team, and not go through the normal review cycle.
Contact the kernel security team for more details on this procedure.
Trees:
- The queues of patches, for both completed versions and in progress
versions can be found at:
http://git.kernel.org/?p=linux/kernel/git/stable/stable-queue.git
- The finalized and tagged releases of all stable kernels can be found
in separate branches per version at:
http://git.kernel.org/?p=linux/kernel/git/stable/linux-stable.git
Review committee:
- This is made up of a number of kernel developers who have volunteered for
this task, and a few that haven't.
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