Re: [PATCH] x86/sgx: Fix deadloop in __sgx_alloc_epc_page()

Jarkko Sakkinen
2024-09-04T14:17:28Z

On Wed Sep 4, 2024 at 4:39 AM EEST, Aaron Lu wrote:
> On Tue, Sep 03, 2024 at 07:05:40PM +0300, Jarkko Sakkinen wrote:
> > On Fri Aug 30, 2024 at 9:14 AM EEST, Aaron Lu wrote:
> > > On Thu, Aug 29, 2024 at 07:44:13PM +0300, Jarkko Sakkinen wrote:
> > > > On Thu Aug 29, 2024 at 5:38 AM EEST, Aaron Lu wrote:
> > > > > When current node doesn't have a EPC section configured by firmware and
> > > > > all other EPC sections memory are used up, CPU can stuck inside the
> > > > > while loop in __sgx_alloc_epc_page() forever and soft lockup will happen.
> > > > > Note how nid_of_current will never equal to nid in that while loop because
> > > > ~~~~
> > > >
> > > > Oh *that* while loop ;-) Please be more specific.
> > >
> > > What about:
> > > Note how nid_of_current will never be equal to nid in the while loop that
> > > searches an available EPC page from remote nodes because nid_of_current is
> > > not set in sgx_numa_mask.
> >
> > That would work I think!
>
> While rewriting the changelog, I find it more natural to explain this
> "while loop" when I first mentioned it, i.e.
>
> When the current node doesn't have an EPC section configured by firmware
> and all other EPC sections are used up, CPU can get stuck inside the
> while loop that looks for an available EPC page from remote nodes
> indefinitely, leading to a soft lockup. Note how nid_of_current will
> never be equal to nid in that while loop because nid_of_current is not
> set in sgx_numa_mask.
>
> I hope this looks fine to you.

Yes, it is. I just want the storyline to the commit message as
a reminder why we did this, that's all. It helps a lot later on
when having to look into commit history.

BR, Jarkko