linux-kernel - Re: [PATCH v8 4/5] x86/mm: Add noalias variants of set_memory

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Date:   Wed, 20 Jul 2022 19:17:51 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Kai Huang <kai.huang@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Wander Lairson Costa <wander@...hat.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 4/5] x86/mm: Add noalias variants of
 set_memory_*crypted() functions

On Wed, Jul 20, 2022 at 07:56:04AM -0700, Sathyanarayanan Kuppuswamy wrote:
> diff --git a/arch/x86/coco/mem.c b/arch/x86/coco/mem.c
> new file mode 100644
> index 000000000000..ef76a8accc1e
> --- /dev/null
> +++ b/arch/x86/coco/mem.c
> @@ -0,0 +1,82 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Confidential Computing Decrypted Memory Allocator
> + *
> + * Copyright (C) 2022 Intel Corporation, Inc.
> + *
> + */
> +
> +#undef pr_fmt
> +#define pr_fmt(fmt)     "cc/mem: " fmt
> +
> +#include <linux/export.h>
> +#include <linux/mm.h>
> +#include <linux/cc_platform.h>
> +#include <linux/set_memory.h>
> +#include <linux/platform_device.h>
> +#include <linux/dma-mapping.h>
> +
> +#include <asm/coco.h>
> +#include <asm/processor.h>
> +
> +#define CC_MEM_DRIVER          "ccmem"
> +
> +struct platform_device *mem_pdev;

'static'?

> +dma_addr_t handle;

Hm. How does it work with >1 allocation a time?

> +
> +/* Allocate decrypted memory of given size */
> +void *cc_decrypted_alloc(size_t size, gfp_t gfp)
> +{
> +       if (!mem_pdev)
> +               return NULL;
> +
> +       return dma_alloc_coherent(&mem_pdev->dev, size, &handle, gfp);
> +}
> +
> +/* Free given decrypted memory */
> +void cc_decrypted_free(void *addr, size_t size)
> +{
> +       if (!mem_pdev)
> +               return;
> +
> +       dma_free_coherent(&mem_pdev->dev, size, addr, handle);
> +}
> +

-- 
 Kirill A. Shutemov