From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-sgx@vger.kernel.org
Subject: Re: [PATCH] x86/sgx: WARN once if EREMOVE fails when killing an enclave
Date: Thu, 10 Oct 2019 13:52:56 -0700 [thread overview]
Message-ID: <20191010205256.GG23798@linux.intel.com> (raw)
In-Reply-To: <20191010185607.GE23798@linux.intel.com>
On Thu, Oct 10, 2019 at 11:56:07AM -0700, Sean Christopherson wrote:
> On Thu, Oct 10, 2019 at 11:35:48AM -0700, Sean Christopherson wrote:
> > On Wed, Oct 09, 2019 at 03:04:50AM +0300, Jarkko Sakkinen wrote:
> > > On Mon, Oct 07, 2019 at 09:13:34PM -0700, Sean Christopherson wrote:
> > > > WARN if EREMOVE fails when destroying an enclave. sgx_encl_release()
> > > > uses the non-WARN __sgx_free_page() when freeing pages as some pages may
> > > > be in the process of being reclaimed, i.e. are owned by the reclaimer.
> > > > But EREMOVE should never fail as sgx_encl_destroy() is only called when
> > > > the enclave cannot have active threads, e.g. prior to EINIT and when the
> > > > enclave is being released.
> > > >
> > > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > >
> > > For me this concludes that I will manually convert all the call sites
> > > to use __sgx_free_page() and add appropriate warnings. I agree with
> > > Borislav's conclusions here.
> >
> > Argh, now we have a bunch of call sites that can silently leak EPC pages,
> > and I'm seeing timeouts during testing that strongly suggest pages are
> > being leaked...
>
> Confirmed that we're leaking pages, but it's not related to the -EBUSY
> case in sgx_free_page(). Debug in progress...
>
> As to the sgx_free_page() thing, I think we can invert the old WARN logic
> and make everyone happy. I'll send a patch.
Figured out what's up. I'm testing in a VM with multiple EPC sections.
Because of a change in v23[*], sgx_nr_free_pages is getting corrupted due
to non-atomic concurrent writes. When it drops below 0 and wraps to a
high value the swap thread stops reclaiming and things grind to a halt.
[*] https://patchwork.kernel.org/patch/11146733/#22887361
prev parent reply other threads:[~2019-10-10 20:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 4:13 [PATCH] x86/sgx: WARN once if EREMOVE fails when killing an enclave Sean Christopherson
2019-10-08 4:15 ` Sean Christopherson
2019-10-09 0:04 ` Jarkko Sakkinen
2019-10-10 18:35 ` Sean Christopherson
2019-10-10 18:56 ` Sean Christopherson
2019-10-10 20:52 ` Sean Christopherson [this message]
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