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

[Greg KH]

On Wed, Apr 15, 2020 at 10:40:05PM +1000, Andrew Donnellan wrote:
> From: Michael Ellerman 
> 
> 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 
> [ajd: Backport to 4.19 tree, CVE-2020-11669]
> Signed-off-by: Andrew Donnellan 
> ---
>  arch/powerpc/kernel/idle_book3s.S | 27 +++
>  1 file changed, 23 insertions(+), 4 deletions(-)

This and the 4.14 patch now queued up, thanks.

greg k-h

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

[Andrew Donnellan]

From: Michael Ellerman 

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 
[ajd: Backport to 4.19 tree, CVE-2020-11669]
Signed-off-by: Andrew Donnellan 
---
 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 36178000a2f2..4a860d3b9229 100644
--- 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)
 
mfcrr5
@@ -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)
 
-- 
2.20.1