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SubjectRe: [PATCH 1/6] x86/sgx: Do not consider unsanitized pages an error
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On Wed, 2022-08-31 at 06:10 +0300, Jarkko Sakkinen wrote:
> On Wed, Aug 31, 2022 at 05:57:22AM +0300, jarkko@kernel.org wrote:
> > On Wed, Aug 31, 2022 at 02:55:52AM +0000, Huang, Kai wrote:
> > > On Wed, 2022-08-31 at 05:44 +0300, jarkko@kernel.org wrote:
> > > > On Wed, Aug 31, 2022 at 02:35:53AM +0000, Huang, Kai wrote:
> > > > > On Wed, 2022-08-31 at 05:15 +0300, jarkko@kernel.org wrote:
> > > > > > On Wed, Aug 31, 2022 at 01:27:58AM +0000, Huang, Kai wrote:
> > > > > > > On Tue, 2022-08-30 at 15:54 -0700, Reinette Chatre wrote:
> > > > > > > > Hi Jarkko,
> > > > > > > >
> > > > > > > > On 8/29/2022 8:12 PM, Jarkko Sakkinen wrote:
> > > > > > > > > In sgx_init(), if misc_register() for the provision device fails, and
> > > > > > > > > neither sgx_drv_init() nor sgx_vepc_init() succeeds, then ksgxd will be
> > > > > > > > > prematurely stopped.
> > > > > > > >
> > > > > > > > I do not think misc_register() is required to fail for the scenario to
> > > > > > > > be triggered (rather use "or" than "and"?). Perhaps just
> > > > > > > > "In sgx_init(), if a failure is encountered after ksgxd is started
> > > > > > > > (via sgx_page_reclaimer_init()) ...".
> > > > > > >
> > > > > > > IMHO "a failure" might be too vague. For instance, failure to sgx_drv_init()
> > > > > > > won't immediately result in ksgxd to stop prematurally. As long as KVM SGX can
> > > > > > > be initialized successfully, sgx_init() still returns 0.
> > > > > > >
> > > > > > > Btw I was thinking whether we should move sgx_page_reclaimer_init() to the end
> > > > > > > of sgx_init(), after we make sure at least one of the driver and the KVM SGX is
> > > > > > > initialized successfully. Then the code change in this patch won't be necessary
> > > > > > > if I understand correctly. AFAICT there's no good reason to start the ksgxd at
> > > > > > > early stage before we are sure either the driver or KVM SGX will work.
> > > > > >
> > > > > > I would focus fixing the existing flow rather than reinventing the flow.
> > > > > >
> > > > > > It can be made to work, and therefore it is IMHO correct action to take.
> > > > >
> > > > > From another perspective, the *existing flow* is the reason which causes this
> > > > > bug. A real fix is to fix the flow itself.
> > > >
> > > > Any existing flow in part of the kernel can have a bug. That
> > > > does not mean that switching flow would be proper way to fix
> > > > a bug.
> > > >
> > > > BR, Jarkko
> > >
> > > Yes but I think this is only true when the flow is reasonable. If the flow
> > > itself isn't reasonable, we should fix the flow (given it's easy to fix AFAICT).
> > >
> > > Anyway, let us also hear from others.
> >
> > The flow can be made to work without issues, which in the
> > context of a bug fix is exactly what a bug fix should do.
> > Not more or less.
> >
> > You don't gain any measurable value for the user with this
> > switch idea.
>
> And besides this not proper way to review patch anyway because you did
> not review the code. 
>

I did review the code, but I couldn't agree on the fix. That's why I expressed
my view here.


> I'll focus on fix what is broken e.g. so that it
> is easy to backport to stable and distro kernels, and call it a day.
> It certainly does not have to make code "perfect", as long as known
> bugs are sorted out.

Why cannot the fix which fixes the flow go to stable?

>
> You are welcome to review the next version of the patch, once I've
> resolved the issues that were pointed out by Reinette, if you still
> see some issue but this type of speculative discussion is frankly just
> wasting everyones time.

Hmm.. Why pointing out a better fix (my perspective of course) is wasting
everyone's time?


--
Thanks,
-Kai


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