NACK/Cmnt: [SRU][Xenial][PATCH v2 0/3] Fix corruption on blocked_vcpu_on_cpu list

[Stefan Bader]

On 20.01.21 11:52, Ioanna Alifieraki wrote:
> On Wed, Jan 20, 2021 at 8:51 AM Stefan Bader <stefan.bader at canonical.com> wrote:
>>
>> On 06.01.21 00:54, Ioanna Alifieraki wrote:
>>> BugLink: https://bugs.launchpad.net/bugs/1908428
>>>
>>> The following 3 patches fix the bug reported in [1].
>>> They are backported to apply on 4.4 kernels.
>>> Backport is required becasue upstream commit
>>> bc22512bb24c(kvm: vmx: rename vmx_pre/post_block to pi_pre/post_block)
>>> which renames  vmx_pre/post_block functions to pi_pre/post_block
>>> is missing from 4.4.
>>> Original patches come from [2] and have been accepted upstream.
>>>
>>> [1] https://marc.info/?l=kvm&m=149559827906211&w=2
>>> [2] https://lore.kernel.org/lkml/20170606105707.23207-1-pbonzini@redhat.com/
>>>
>>> Paolo Bonzini (3):
>>>   KVM: VMX: extract __pi_post_block
>>>   KVM: VMX: avoid double list add with VT-d posted interrupts
>>>   KVM: VMX: simplify and fix vmx_vcpu_pi_load
>>>
>>>  arch/x86/kvm/vmx.c | 177 ++++++++++++++++++++++-----------------------
>>>  1 file changed, 87 insertions(+), 90 deletions(-)
>>>
>>
>> The first patch appears like it can be safely ignored from a change point of
>> view as it effectively just moves a code section into its own function.
>> The other 2 are rather obscure in what is getting changed. What I mean is that
>> its hard to tell what this code does anyway. So I would rely more on the
>> successful testing. On the regression potential: if you have more insights on
>> how a regression might show up, that should be rather mentioned. Very vaguely
>> this changes around vCPU hotplug(?), so in that case regression potential would
>> be issues in other cases of vCPU addition/removal...
>>
>> Acked-by: Stefan Bader <stefan.bader at canonical.com>
>>
> 
> Thanks for the feedback. I cannot reproduce the bug myself. The user
> that reported the bug
> has tested and so far they don't have mentioned any regression.
> FYI, after exchanging a couple of emails with William I sent a version
> 3 of the patches on Jan 18
> with subject :
> [SRU][Xenial][PATCH v3 0/4] Fix corruption on blocked_vcpu_on_cpu list
> 
> I don't know how you handle these cases in the kernel team. Both v2
> and v3 are functionally
> the same, in v3 the backport is more straightforward because I pull in
> an extra commit.
> 
It is not only me but sometimes also me. But generally to help us, please if
there is a v{x}+1 make sure that all previous threads have a final NACK reply.
Otherwise you get people, like me, looking into the wrong version, realizing the
next morning that they wasted time, getting grumpy and confused. And that won't
help either side. ;)

-Stefan


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