linux-kernel - Re: [PATCH 1/2] platform/x86/amd/pmf: Do not use readl() for policy buffer access

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Message-ID: <7867a727-9bdf-2e48-2a90-c1f31b312c9f@linux.intel.com>
Date: Tue, 27 Feb 2024 16:09:41 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Armin Wolf <W_Armin@....de>
cc: Shyam-sundar.S-k@....com, Hans de Goede <hdegoede@...hat.com>, 
    platform-driver-x86@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] platform/x86/amd/pmf: Do not use readl() for policy
 buffer access

On Tue, 27 Feb 2024, Armin Wolf wrote:

> The policy buffer is allocated using normal memory allocation
> functions, so readl() should not be used on it.
> 
> Compile-tested only.
> 
> Signed-off-by: Armin Wolf <W_Armin@....de>
> ---
>  drivers/platform/x86/amd/pmf/tee-if.c | 4 ++--
>  1 file changed, 2 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..70d09103ab18 100644
> --- a/drivers/platform/x86/amd/pmf/tee-if.c
> +++ b/drivers/platform/x86/amd/pmf/tee-if.c
> @@ -249,8 +249,8 @@ 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 = dev->policy_buf[POLICY_COOKIE_OFFSET];
> +	length = dev->policy_buf[POLICY_COOKIE_LEN];

Hmm, the next question is, is it okay to get just 8 bits instead the full 
dword (the policy_buf is unsigned char *)?

-- 
 i.