linux-kernel - Re: [PATCH] tpm: tpm2-space: Resize session and context buffers dynamically

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Message-ID: <20200625212453.GB20341@linux.intel.com>
Date:   Fri, 26 Jun 2020 00:24:53 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Stefan Berger <stefanb@...ux.ibm.com>
Cc:     linux-integrity@...r.kernel.org,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Sumit Garg <sumit.garg@...aro.org>,
        Alexey Klimov <aklimov@...hat.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: tpm2-space: Resize session and context buffers
 dynamically

On Thu, Jun 25, 2020 at 08:13:09AM -0400, Stefan Berger wrote:
> On 6/25/20 12:24 AM, Jarkko Sakkinen wrote:
> > Re-allocate context and session buffers when needed. Scale them in page
> > increments so that the reallocation is only seldomly required, and thus
> > causes minimal stress to the system. Add a static maximum limit of four
> > pages for buffer sizes.
> > 
> > Cc: James Bottomley <James.Bottomley@...senPartnership.com>
> > Suggested-by: Stefan Berger <stefanb@...ux.ibm.com>
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> > ---
> > Tested only for compilation.
> >   drivers/char/tpm/tpm2-space.c | 80 ++++++++++++++++++++++++-----------
> >   include/linux/tpm.h           |  6 ++-
> >   2 files changed, 59 insertions(+), 27 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> > index 982d341d8837..acb9e82bf9e8 100644
> > --- a/drivers/char/tpm/tpm2-space.c
> > +++ b/drivers/char/tpm/tpm2-space.c
> > @@ -15,6 +15,8 @@
> >   #include <asm/unaligned.h>
> >   #include "tpm.h"
> > +#define TPM2_SPACE_MAX_BUFFER_SIZE	(4 * PAGE_SIZE)
> 
> PAGE_SIZE is 64k on ppc64. Rather use 4 * 4096?

Better to then just put it as 16384.

/Jarkko