From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: "Christopherson, Sean J" <sean.j.christopherson@intel.com>
Cc: "intel-sgx-kernel-dev@lists.01.org"
<intel-sgx-kernel-dev@lists.01.org>,
"platform-driver-x86@vger.kernel.org"
<platform-driver-x86@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Darren Hart <dvhart@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andy Shevchenko <andy@infradead.org>
Subject: Re: [intel-sgx-kernel-dev] [PATCH v7 4/8] intel_sgx: driver for Intel Software Guard Extensions
Date: Thu, 7 Dec 2017 18:12:39 +0200 [thread overview]
Message-ID: <20171207161239.ai7ewjjpi7ivlac6@linux.intel.com> (raw)
In-Reply-To: <20171207160548.doovfdh2lqg5brm3@linux.intel.com>
On Thu, Dec 07, 2017 at 06:05:48PM +0200, Jarkko Sakkinen wrote:
> On Thu, Dec 07, 2017 at 02:46:39PM +0000, Christopherson, Sean J wrote:
> > > + for (i = 0; i < 2; i++) {
> > > + va_page = list_first_entry(&encl->va_pages,
> > > + struct sgx_va_page, list);
> > > + va_offset = sgx_alloc_va_slot(va_page);
> > > + if (va_offset < PAGE_SIZE)
> > > + break;
> > > +
> > > + list_move_tail(&va_page->list, &encl->va_pages);
> > > + }
> >
> > This is broken, there is no guarantee that the next VA page will have
> > a free slot. You have to walk over all VA pages to guarantee a slot
> > is found, e.g. this caused EWB and ELDU errors.
>
> I did run some extensive stress tests on this and did not experience any
> issues. Full VA pages are always put to the end. Please point me to the
> test where this breaks so that I can fix the issue if it persists.
>
> > Querying list.next to determine if an encl_page is resident in the EPC
> > is ugly and unintuitive, and depending on list's internal state seems
> > dangerous. Why not use a flag in the encl_page, e.g. as in the patch
> > I submitted almost 8 months ago for combining epc_page and va_page into
> > a union? And, the encl's SGX_ENCL_SECS_EVICTED flag can be dropped if
> > a flag is added to indicate whether or not any encl_page is resident in
> > the EPC.
> >
> > https://lists.01.org/pipermail/intel-sgx-kernel-dev/2017-April/000570.html
>
> I think it is better to just zero list entry and do list_empty test. You
> correct that checking that with poison is ugly.
>
> Last flag bit wll be needed for the SGX_ENCL_PAGE_TRIM. It is useful to
> have the flag in the enclave in order to be able to pack struct
> sgx_encl_page.
Most of the discussion was in the first version of that patch set. If
you think that I miss to apply something relevant, please ping me rather
than wait eight months.
/Jarkko
next prev parent reply other threads:[~2017-12-07 16:12 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-07 1:54 [PATCH v7 0/8] Intel SGX Driver Jarkko Sakkinen
2017-12-07 1:54 ` [PATCH v7 1/8] intel_sgx: updated MAINTAINERS Jarkko Sakkinen
2017-12-07 1:54 ` [PATCH v7 2/8] x86: add SGX definitions to cpufeature Jarkko Sakkinen
2017-12-07 1:54 ` [PATCH v7 3/8] x86: add SGX definitions to msr-index.h Jarkko Sakkinen
2017-12-07 1:54 ` [PATCH v7 4/8] intel_sgx: driver for Intel Software Guard Extensions Jarkko Sakkinen
2017-12-07 14:46 ` [intel-sgx-kernel-dev] " Christopherson, Sean J
2017-12-07 16:05 ` Jarkko Sakkinen
2017-12-07 16:12 ` Jarkko Sakkinen [this message]
2017-12-08 15:31 ` Christopherson, Sean J
2017-12-14 12:42 ` Jarkko Sakkinen
2017-12-12 21:32 ` Sean Christopherson
2017-12-14 13:03 ` Jarkko Sakkinen
[not found] ` <37306EFA9975BE469F115FDE982C075BC6B39E1D@ORSMSX108.amr.corp.intel.com>
2017-12-12 21:46 ` Sean Christopherson
2017-12-14 13:10 ` Jarkko Sakkinen
2017-12-14 21:36 ` Christopherson, Sean J
2017-12-15 15:02 ` Jarkko Sakkinen
2017-12-12 7:42 ` Ayoun, Serge
2017-12-07 1:54 ` [PATCH v7 5/8] intel_sgx: ptrace() support Jarkko Sakkinen
2017-12-07 1:54 ` [PATCH v7 6/8] intel_sgx: driver documentation Jarkko Sakkinen
2017-12-07 1:54 ` [PATCH v7 7/8] fs/pipe.c: export create_pipe_files() Jarkko Sakkinen
2017-12-07 1:54 ` [PATCH v7 8/8] intel_sgx: in-kernel launch enclave Jarkko Sakkinen
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