linux-kernel - Re: [PATCH v4 3/8] optee: fix tee out of memory failure seen during kexec reboot

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Date:   Mon, 14 Jun 2021 09:21:07 +0200
From:   Jens Wiklander <jens.wiklander@...aro.org>
To:     Tyler Hicks <tyhicks@...ux.microsoft.com>
Cc:     Allen Pais <apais@...ux.microsoft.com>,
        Sumit Garg <sumit.garg@...aro.org>,
        Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Vikas Gupta <vikas.gupta@...adcom.com>,
        Thirupathaiah Annapureddy <thiruan@...rosoft.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Rafał Miłecki <zajec5@...il.com>,
        OP-TEE TrustedFirmware <op-tee@...ts.trustedfirmware.org>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        bcm-kernel-feedback-list@...adcom.com, linux-mips@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/8] optee: fix tee out of memory failure seen during
 kexec reboot

On Fri, Jun 11, 2021 at 07:53:26AM -0500, Tyler Hicks wrote:
> On 2021-06-11 11:11:33, Jens Wiklander wrote:
> > On Thu, Jun 10, 2021 at 11:09 PM Tyler Hicks
> > <tyhicks@...ux.microsoft.com> wrote:
> > >
> > > From: Allen Pais <apais@...ux.microsoft.com>
> > >
> > > The following out of memory errors are seen on kexec reboot
> > > from the optee core.
> > >
> > > [    0.368428] tee_bnxt_fw optee-clnt0: tee_shm_alloc failed
> > > [    0.368461] tee_bnxt_fw: probe of optee-clnt0 failed with error -22
> > >
> > > tee_shm_release() is not invoked on dma shm buffer.
> > >
> > > Implement .shutdown() method to handle the release of the buffers
> > > correctly.
> > >
> > > More info:
> > > https://github.com/OP-TEE/optee_os/issues/3637
> > >
> > > Signed-off-by: Allen Pais <apais@...ux.microsoft.com>
> > > Reviewed-by: Tyler Hicks <tyhicks@...ux.microsoft.com>
> > 
> > Do we really need this considering the patch "optee: Refuse to load
> > the driver under the kdump kernel"?
> 
> Yes. That patch fixes boot hangs when all of the OP-TEE threads were in
> the suspended state at the time of a kernel panic. The kexec into the
> kdump kernel after a panic is an "emergency" kexec that doesn't even
> call .shutdown hooks. There's no way for the OP-TEE driver to clean up
> after itself.
> 
> This patch disables the shm cache (and unregisters the shm buffers)
> during a normal kexec from one perfectly working kernel into a new
> kernel. This is required because the new kernel will not be able to
> handle the virtual addresses that were cached under the old kernel. The
> new kernel has an entirely different memory layout and the old addresses
> point to unmapped memory or memory that's mapped but probably not a TEE
> shm.

Got it, thanks.

Jens