[SRU][Bionic][PATCH v2] powerpc/powernv/idle: Restore AMR/UAMOR/AMOR after idle

[Juerg Haefliger]

From: Michael Ellerman <mpe at ellerman.id.au>

BugLink: https://bugs.launchpad.net/bugs/1874005

In order to implement KUAP (Kernel Userspace Access Protection) on
Power9 we will be using the AMR, and therefore indirectly the
UAMOR/AMOR.

So save/restore these regs in the idle code.

Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

(cherry picked from commit 53a712bae5dd919521a58d7bad773b949358add0)
Signed-off-by: Juerg Haefliger <juergh at canonical.com>
---
 arch/powerpc/kernel/idle_book3s.S | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 785d67255b29..a02e7f2a2f65 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -168,8 +168,11 @@ core_idle_lock_held:
 	bne-	core_idle_lock_held
 	blr
 
-/* Reuse an unused pt_regs slot for IAMR */
+/* Reuse some unused pt_regs slots for AMR/IAMR/UAMOR/UAMOR */
+#define PNV_POWERSAVE_AMR	_TRAP
 #define PNV_POWERSAVE_IAMR	_DAR
+#define PNV_POWERSAVE_UAMOR	_DSISR
+#define PNV_POWERSAVE_AMOR	RESULT
 
 /*
  * Pass requested state in r3:
@@ -203,8 +206,16 @@ pnv_powersave_common:
 	SAVE_NVGPRS(r1)
 
 BEGIN_FTR_SECTION
+	mfspr	r4, SPRN_AMR
 	mfspr	r5, SPRN_IAMR
+	mfspr	r6, SPRN_UAMOR
+	std	r4, PNV_POWERSAVE_AMR(r1)
 	std	r5, PNV_POWERSAVE_IAMR(r1)
+	std	r6, PNV_POWERSAVE_UAMOR(r1)
+BEGIN_FTR_SECTION_NESTED(42)
+	mfspr	r7, SPRN_AMOR
+	std	r7, PNV_POWERSAVE_AMOR(r1)
+END_FTR_SECTION_NESTED_IFSET(CPU_FTR_HVMODE, 42)
 END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 
 	mfcr	r5
@@ -968,12 +979,20 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
 	REST_GPR(2, r1)
 
 BEGIN_FTR_SECTION
-	/* IAMR was saved in pnv_powersave_common() */
+	/* These regs were saved in pnv_powersave_common() */
+	ld	r4, PNV_POWERSAVE_AMR(r1)
 	ld	r5, PNV_POWERSAVE_IAMR(r1)
+	ld	r6, PNV_POWERSAVE_UAMOR(r1)
+	mtspr	SPRN_AMR, r4
 	mtspr	SPRN_IAMR, r5
+	mtspr	SPRN_UAMOR, r6
+BEGIN_FTR_SECTION_NESTED(42)
+	ld	r7, PNV_POWERSAVE_AMOR(r1)
+	mtspr	SPRN_AMOR, r7
+END_FTR_SECTION_NESTED_IFSET(CPU_FTR_HVMODE, 42)
 	/*
-	 * We don't need an isync here because the upcoming mtmsrd is
-	 * execution synchronizing.
+	 * We don't need an isync here after restoring IAMR because the upcoming
+	 * mtmsrd is execution synchronizing.
 	 */
 END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 
-- 
2.20.1