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

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Message-ID: <334a40d3-452b-4df1-a2ed-c79b87be086f@linux.intel.com>
Date:   Wed, 20 Jul 2022 09:58:42 -0700
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...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 7/20/22 9:17 AM, Kirill A. Shutemov wrote:
> 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'?

Agree.

> 
>> +dma_addr_t handle;
> 
> Hm. How does it work with >1 allocation a time?

It is a bug. I think we should make it as parameter to alloc/free APIs.

> 
>> +
>> +/* 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);
>> +}
>> +
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer