linux-kernel - [PATCH 4.14 36/95] powerpc/kexec: Fix kexec/kdump in P9 guest kernels

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Date:   Mon,  4 Dec 2017 17:00:00 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yilin Zhang <yilzhang@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Balbir Singh <bsingharora@...il.com>,
        David Gibson <david@...son.dropbear.id.au>
Subject: [PATCH 4.14 36/95] powerpc/kexec: Fix kexec/kdump in P9 guest kernels

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Ellerman <mpe@...erman.id.au>

commit 2621e945fbf1d6df5f3f0ba7be5bae3d2cf9b6a5 upstream.

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")
Reported-by: Yilin Zhang <yilzhang@...hat.com>
Debugged-by: David Gibson <david@...son.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Acked-by: Balbir Singh <bsingharora@...il.com>
Reviewed-by: David Gibson <david@...son.dropbear.id.au>
Tested-by: David Gibson <david@...son.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/kernel/misc_64.S |    2 ++
 1 file changed, 2 insertions(+)

--- 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.