Re: [PATCH v5 02/10] powerpc/powernv/idle: Restore AMR/UAMOR/AMOR after idle

[Michael Ellerman]

Akshay Adiga  writes:

> On Fri, Mar 08, 2019 at 12:16:11PM +1100, Michael Ellerman wrote:
>> 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 
>> ---
>> v5: Unchanged.
>> v4: New.
>> 
>>  arch/powerpc/kernel/idle_book3s.S | 27 +++
>>  1 file changed, 23 insertions(+), 4 deletions(-)
>
> Opps.. i posted a comment on the v4. 
>
> It would be good if we can make AMOR/UAMOR/AMR save-restore
> code power9 only.

Yes that would be a good optimisation.

If you can send an incremental patch against this one I'll squash it in.
If not I'll try and get it done at some point before merging.

cheers

Re: [PATCH v5 02/10] powerpc/powernv/idle: Restore AMR/UAMOR/AMOR after idle

[Akshay Adiga]

On Fri, Mar 08, 2019 at 12:16:11PM +1100, Michael Ellerman wrote:
> 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 
> ---
> v5: Unchanged.
> v4: New.
> 
>  arch/powerpc/kernel/idle_book3s.S | 27 +++
>  1 file changed, 23 insertions(+), 4 deletions(-)

Opps.. i posted a comment on the v4. 

It would be good if we can make AMOR/UAMOR/AMR save-restore
code power9 only.

[PATCH v5 02/10] powerpc/powernv/idle: Restore AMR/UAMOR/AMOR after idle

[Michael Ellerman]

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 
---
v5: Unchanged.
v4: New.

 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 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
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 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
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