Re: [PATCH v3 1/2] tpm: Use GFP_KERNEL for allocating struct tpm_buf

From: Jarkko Sakkinen
Date: Tue Oct 08 2019 - 18:52:09 EST

On Mon, Oct 07, 2019 at 12:12:08PM -0700, James Bottomley wrote:
> From: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> 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@xxxxxxxxxxxxxxxxxxxxx>

Thanks a lot. Makes a lot more sense than the patch that I sent.

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>