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s390: Remove 'message security assist' from the list of vital facilities

RFC PATCH Heiko Carstens 1 participant 1 message May 23, 2017 1 message not in the archive s390

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Heiko Carstens

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Quoted 9 lines · Thomas Huth

The code in arch/s390/crypto checks for the availability of the 'message security assist' facility on its own, either by using module_cpu_feature_match(MSA, ...) or by checking the facility bit during cpacf_query(). Thus setting the MSA facility bit in gen_facilities.c as hard requirement is not necessary. We can remove it here, so that the kernel can also run on systems that do not provide the MSA facility yet (like the emulated environment of QEMU, for example).

Quoted 7 lines
Signed-off-by Thomas Huth <[email protected]>

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Note: Not sure whether I've missed something here and the facility is urgently required somewhere else, where the code does not have these additional checks like in arch/s390/crypto - that's why I've marked the patch with "RFC" ... so if anybody has more insights, please let me know!

That bit was part of the initial conversion from machine type to
facilities: 8c4caa4fbfc1 ("[S390] use facility list for cpu type safety check"). However even that old code did have a facility check for bit 17 within the crypto code.

arch/s390/tools/gen_facilities.c struct facility_def { · line 38

Quoted 12 lines
 arch/s390/tools/gen_facilities.c | 1 -
 1 file changed, 1 deletion(-)
arch/s390/tools/gen_facilities.c +0 -1
index be63fbd..cfe3f76 100644
@@ -35,7 +35,6 @@ struct facility_def {
 #endif
 #ifdef CONFIG_HAVE_MARCH_Z9_109_FEATURES
 			7,  /* stfle */
-			17, /* message security assist */

We could also remove the stfle bit, since the kernel also always checks if it is available before executing the instructions.

Looking at the facility list: stfle is the only odd one left. So I will remove that one as well.

Applied your patch. Thanks!