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powerpc/book3s64/keys/kuap: Reset AMR/IAMR values on kexec

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As we kexec across kernels that use AMR/IAMR for different purposes
we need to ensure that new kernels get kexec'd with a reset value
of AMR/IAMR. For ex: the new kernel can use key 0 for kernel mapping and the old
AMR value prevents access to key 0.

This patch also removes reset if IAMR and AMOR in kexec_sequence. Reset of AMOR
is not needed and the IAMR reset is partial (it doesn't do the reset
on secondary cpus) and is redundant with this patch.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200709032946.881753-19-aneesh.kumar@linux.ibm.com
This commit is contained in:
Aneesh Kumar K.V
2020-07-09 08:59:41 +05:30
committed by Michael Ellerman
parent 7cdd3745f2
commit 000a42b35a
5 changed files with 40 additions and 14 deletions
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14
arch/powerpc/kernel/misc_64.S
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@@ -413,20 +413,6 @@ _GLOBAL(kexec_sequence)
li r0,0
std r0,16(r1)
BEGIN_FTR_SECTION
/*
* This is the best time to turn AMR/IAMR off.
* key 0 is used in radix for supervisor<->user
* protection, but on hash key 0 is reserved
* ideally we want to enter with a clean state.
* NOTE, we rely on r0 being 0 from above.
*/
mtspr SPRN_IAMR,r0
BEGIN_FTR_SECTION_NESTED(42)
mtspr SPRN_AMOR,r0
END_FTR_SECTION_NESTED_IFSET(CPU_FTR_HVMODE, 42)
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
/* save regs for local vars on new stack.
* yes, we won't go back, but ...
*/