Re: [PATCH v1 1/1] powerpc/papr_scm: Properly handle UUID types and API

From: Aneesh Kumar K.V
Date: Fri Apr 16 2021 - 03:58:57 EST

On 4/15/21 7:16 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 fix Sparse warnings about assigning strict types to POD.

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")
Cc: Oliver O'Halloran <oohall@xxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Not tested
arch/powerpc/platforms/pseries/papr_scm.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index ae6f5d80d5ce..4366e1902890 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -1085,8 +1085,9 @@ 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 */
@@ -1129,16 +1130,18 @@ 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
+ * we store a raw buffer 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.
- 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]);

ok that does the equivalent of cpu_to_le64 there. So we are good. But the comment update is missing the details why we did that get_unaligned_le64. Maybe raw buffer representation is the correct term?
Should we add an example in the comment. ie,

* Historically we stored the cookie in the below format.
for a uuid str 72511b67-0b3b-42fd-8d1d-5be3cae8bcaa
cookie1 was 0xfd423b0b671b5172 cookie2 was 0xaabce8cae35b1d8d

/* might be zero */
p->metadata_size = metadata_size;