powerpc/kexec: Fix kexec/kdump in P9 guest kernels

The code that cleans up the IAMR/AMOR before kexec'ing failed to
remember that when we're running as a guest AMOR is not writable, it's
hypervisor privileged.

They symptom is that the kexec stops before entering purgatory and
nothing else is seen on the console. If you examine the state of the
system all threads will be in the 0x700 program check handler.

Fix it by making the write to AMOR dependent on HV mode.

Fixes: 1e2a516e89fc ("powerpc/kexec: Fix radix to hash kexec due to IAMR/AMOR")
Cc: stable@vger.kernel.org # v4.10+
Reported-by: Yilin Zhang <yilzhang@redhat.com>
Debugged-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Tested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index 8ac0bd2bddb0c93b95dccfd61807807219913b5e..3280953a82cf63c4372735762a09804fd9c21677 100644 (file)
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -623,7 +623,9 @@ BEGIN_FTR_SECTION
         * 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.