linux-kernel - Re: [PATCH v3 1/2] tpm: Use GFP_KERNEL for allocating struct tpm

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Message-ID: <20191007234323.bzeov5mpc4xregcy@cantor>
Date:   Mon, 7 Oct 2019 16:43:23 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     James Bottomley <jejb@...ux.ibm.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-integrity@...r.kernel.org, Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] tpm: Use GFP_KERNEL for allocating struct tpm_buf

On Mon Oct 07 19, James Bottomley wrote:
>From: James Bottomley <James.Bottomley@...senPartnership.com>
>Subject: [PATCH] tpm: use GFP kernel for tpm_buf allocations
>
>The current code uses GFP_HIGHMEM, which is wrong because GFP_HIGHMEM
>(on 32 bit systems) is memory ordinarily inaccessible to the kernel
>and should only be used for allocations affecting userspace.  In order
>to make highmem visible to the kernel on 32 bit it has to be kmapped,
>which consumes valuable entries in the kmap region.  Since the tpm_buf
>is only ever used in the kernel, switch to using a GFP_KERNEL
>allocation so as not to waste kmap space on 32 bits.
>
>Fixes: a74f8b36352e (tpm: introduce tpm_buf)
>Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
>---

Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>