Re: [PATCH 1/1] mm: disable CONFIG_PER_VMA_LOCK by default until its fixed

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 7/4/23 10:12, Linux regression tracking (Thorsten Leemhuis) wrote:
> [CCing the regression list]
> 
> On 03.07.23 20:21, Suren Baghdasaryan wrote:
>> A memory corruption was reported in [1] with bisection pointing to the
>> patch [2] enabling per-VMA locks for x86.
>> Disable per-VMA locks config to prevent this issue while the problem is
>> being investigated. This is expected to be a temporary measure.
> 
> I have to wonder: is disabling by default sufficient here? Sure, it's a
> new feature, so once this change is merged and backported to 6.4.y it's
> not regression for anyone that will do the jump from older kernels to
> 6.4.y and run oldconfig.
> 
> But how about those that did the jump already or will do so before the
> fix is backported (it's possible that Arch Linux and openSUSE Tumblweed
> do this; and there is a certain chance that Fedora already has
> CONFIG_PER_VMA_LOCK enabled in their 6.4 configs, too)? This sounds to
> me like many of those will have CONFIG_PER_VMA_LOCK enabled in their
> configs now. And unless I'm missing something switching the default
> won't turn it off next time they run make oldconfig -- or will it? So
> for them the regression won't be fixed (unless they fiddle manually with
> their configuration, but they shouldn't do so to fix a regression).
> 
> Or is my logic mistaken somewhere?

Your logic is correct I just tried Suren's patch with my local tree and
it did not change a thing.

If you have an existing .config this patch does nothing.

Regards,

Hans





> 
>> [1] https://bugzilla.kernel.org/show_bug.cgi?id=217624
> 
> Side note: that should be a proper Link: or Closes: tag as described in
> Documentation/process/submitting-patches.rst or
> Documentation/process/5.Posting.rst -- and it should be close to the
> Reported-by: tag (checkpatch.pl should have mentioned that).
> 
> E.g. like this:
> 
>> [2] https://lore.kernel.org/all/20230227173632.3292573-30-surenb@google.com
>>
>> Reported-by: Jiri Slaby <jirislaby@kernel.org>
> Closes:
> https://lore.kernel.org/lkml/dbdef34c-3a07-5951-e1ae-e9c6e3cdf51b@kernel.org/
>> Reported-by: Jacob Young <jacobly.alt@gmail.com>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217624 [1]
>> Fixes: 0bff0aaea03e ("x86/mm: try VMA lock-based page fault handling first")
>> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> 
>> [...]
> 
> Ciao, Thorsten
>