linux-kernel - Re: [PATCH, RFC 26/62] keys/mktme: Move the MKTME payload into a cache aligned structure

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Date:   Fri, 14 Jun 2019 13:35:23 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Alison Schofield <alison.schofield@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC 26/62] keys/mktme: Move the MKTME payload into a
 cache aligned structure

On Wed, May 08, 2019 at 05:43:46PM +0300, Kirill A. Shutemov wrote:

> +/* Copy the payload to the HW programming structure and program this KeyID */
> +static int mktme_program_keyid(int keyid, struct mktme_payload *payload)
> +{
> +	struct mktme_key_program *kprog = NULL;
> +	int ret;
> +
> +	kprog = kmem_cache_zalloc(mktme_prog_cache, GFP_ATOMIC);

Why GFP_ATOMIC, afaict neither of the usage is with a spinlock held.

> +	if (!kprog)
> +		return -ENOMEM;
> +
> +	/* Hardware programming requires cached aligned struct */
> +	kprog->keyid = keyid;
> +	kprog->keyid_ctrl = payload->keyid_ctrl;
> +	memcpy(kprog->key_field_1, payload->data_key, MKTME_AES_XTS_SIZE);
> +	memcpy(kprog->key_field_2, payload->tweak_key, MKTME_AES_XTS_SIZE);
> +
> +	ret = MKTME_PROG_SUCCESS;	/* Future programming call */
> +	kmem_cache_free(mktme_prog_cache, kprog);
> +	return ret;
> +}