linux-kernel - Re: [PATCH v2 1/1] powerpc/papr_scm: Properly handle UUID types and API

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Date:   Wed, 16 Jun 2021 19:17:03 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "Oliver O'Halloran" <oohall@...il.com>
Subject: Re: [PATCH v2 1/1] powerpc/papr_scm: Properly handle UUID types and
 API

On 6/16/21 7:13 PM, Andy Shevchenko wrote:
> Parse to and export from UUID own type, before dereferencing.
> This also fixes wrong comment (Little Endian UUID is something else)
> and should eliminate the direct strict types assignments.
> 
> Fixes: 43001c52b603 ("powerpc/papr_scm: Use ibm,unit-guid as the iset cookie")
> Fixes: 259a948c4ba1 ("powerpc/pseries/scm: Use a specific endian format for storing uuid from the device tree")


Do we need the Fixes: there? It didn't change any functionality right? 
The format with which we stored cookie1 remains the same with older and 
newer code. The newer one is better?

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>

> Cc: Oliver O'Halloran <oohall@...il.com>
> Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
> v2: added missed header (Vaibhav), updated comment (Aneesh),
>      rewrite part of the commit message to avoid mentioning the Sparse
>   arch/powerpc/platforms/pseries/papr_scm.c | 27 +++++++++++++++--------
>   1 file changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
> index e2b69cc3beaf..b43be41e8ff7 100644
> --- a/arch/powerpc/platforms/pseries/papr_scm.c
> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> @@ -18,6 +18,7 @@
>   #include <asm/plpar_wrappers.h>
>   #include <asm/papr_pdsm.h>
>   #include <asm/mce.h>
> +#include <asm/unaligned.h>
>   
>   #define BIND_ANY_ADDR (~0ul)
>   
> @@ -1101,8 +1102,9 @@ static int papr_scm_probe(struct platform_device *pdev)
>   	u32 drc_index, metadata_size;
>   	u64 blocks, block_size;
>   	struct papr_scm_priv *p;
> +	u8 uuid_raw[UUID_SIZE];
>   	const char *uuid_str;
> -	u64 uuid[2];
> +	uuid_t uuid;
>   	int rc;
>   
>   	/* check we have all the required DT properties */
> @@ -1145,16 +1147,23 @@ static int papr_scm_probe(struct platform_device *pdev)
>   	p->hcall_flush_required = of_property_read_bool(dn, "ibm,hcall-flush-required");
>   
>   	/* We just need to ensure that set cookies are unique across */
> -	uuid_parse(uuid_str, (uuid_t *) uuid);
> +	uuid_parse(uuid_str, &uuid);
> +
>   	/*
> -	 * cookie1 and cookie2 are not really little endian
> -	 * we store a little endian representation of the
> -	 * uuid str so that we can compare this with the label
> -	 * area cookie irrespective of the endian config with which
> -	 * the kernel is built.
> +	 * The cookie1 and cookie2 are not really little endian.
> +	 * We store a raw buffer representation of the
> +	 * uuid string so that we can compare this with the label
> +	 * area cookie irrespective of the endian configuration
> +	 * with which the kernel is built.
> +	 *
> +	 * Historically we stored the cookie in the below format.
> +	 * for a uuid string 72511b67-0b3b-42fd-8d1d-5be3cae8bcaa
> +	 *	cookie1 was 0xfd423b0b671b5172
> +	 *	cookie2 was 0xaabce8cae35b1d8d
>   	 */
> -	p->nd_set.cookie1 = cpu_to_le64(uuid[0]);
> -	p->nd_set.cookie2 = cpu_to_le64(uuid[1]);
> +	export_uuid(uuid_raw, &uuid);
> +	p->nd_set.cookie1 = get_unaligned_le64(&uuid_raw[0]);
> +	p->nd_set.cookie2 = get_unaligned_le64(&uuid_raw[8]);
>   
>   	/* might be zero */
>   	p->metadata_size = metadata_size;
>