linux-kernel - Re: [PATCH v2 2/3] platform/x86/amd/pmf: Do not use readl() for policy buffer access

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Date: Tue, 27 Feb 2024 14:59:23 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Armin Wolf <W_Armin@....de>
cc: Shyam-sundar.S-k@....com, 
    Mika Westerberg <mika.westerberg@...ux.intel.com>, 
    sathyanarayanan.kuppuswamy@...ux.intel.com, 
    Hans de Goede <hdegoede@...hat.com>, platform-driver-x86@...r.kernel.org, 
    LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] platform/x86/amd/pmf: Do not use readl() for
 policy buffer access

On Fri, 23 Feb 2024, Armin Wolf wrote:

> The policy buffer is allocated using normal memory allocation
> functions, so readl() should not be used on it.
> 
> Use get_unaligned_le32() instead.
> 
> Compile-tested only.
> 
> Signed-off-by: Armin Wolf <W_Armin@....de>
> ---
>  drivers/platform/x86/amd/pmf/tee-if.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/x86/amd/pmf/tee-if.c b/drivers/platform/x86/amd/pmf/tee-if.c
> index 16973bebf55f..3220b6580270 100644
> --- a/drivers/platform/x86/amd/pmf/tee-if.c
> +++ b/drivers/platform/x86/amd/pmf/tee-if.c
> @@ -11,6 +11,7 @@
>  #include <linux/debugfs.h>
>  #include <linux/tee_drv.h>
>  #include <linux/uuid.h>
> +#include <asm/unaligned.h>
>  #include "pmf.h"
> 
>  #define MAX_TEE_PARAM	4
> @@ -249,8 +250,8 @@ static int amd_pmf_start_policy_engine(struct amd_pmf_dev *dev)
>  	u32 cookie, length;
>  	int res;
> 
> -	cookie = readl(dev->policy_buf + POLICY_COOKIE_OFFSET);
> -	length = readl(dev->policy_buf + POLICY_COOKIE_LEN);
> +	cookie = get_unaligned_le32(dev->policy_buf + POLICY_COOKIE_OFFSET);
> +	length = get_unaligned_le32(dev->policy_buf + POLICY_COOKIE_LEN);

I don't understand you need _unaligned_ here, the offsets should be dword 
aligned, no?

#define POLICY_COOKIE_OFFSET      0x10
#define POLICY_COOKIE_LEN         0x14

-- 
 i.