[PATCH 4.19 124/146] powerpc/powernv/idle: Restore AMR/UAMOR/AMOR after idle

From: Greg Kroah-Hartman
Date: Thu Apr 16 2020 - 11:52:56 EST


From: Michael Ellerman <mpe@xxxxxxxxxxxxxx>

commit 53a712bae5dd919521a58d7bad773b949358add0 upstream.

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@xxxxxxxxxxxxxx>
[ajd: Backport to 4.19 tree, CVE-2020-11669]
Signed-off-by: Andrew Donnellan <ajd@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/idle_book3s.S | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)

--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -170,8 +170,11 @@ 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:
@@ -205,8 +208,16 @@ 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
@@ -935,12 +946,20 @@ 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)