Re: [PATCH] tpm: Detach page allocation from tpm_buf

[James Bottomley]

On Wed, 2019-09-25 at 16:48 +0300, Jarkko Sakkinen wrote:
[...]
> +	data_page = alloc_page(GFP_HIGHUSER);
> +	if (!data_page)
> +		return -ENOMEM;
> +
> +	data_ptr = kmap(data_page);

I don't think this is such a good idea.  On 64 bit it's no different
from GFP_KERNEL and on 32 bit where we do have highmem, kmap space is
at a premium, so doing a highmem allocation + kmap is more wasteful of
resources than simply doing GFP_KERNEL.  In general, you should only do
GFP_HIGHMEM if the page is going to be mostly used by userspace, which
really isn't the case here.

James