powerpc/64: Convert fast_exception_return to use RFI_TO_USER/KERNEL

[ Upstream commit a08f828cf47e6c605af21d2cdec68f84e799c318 ]

Similar to the syscall return path, in fast_exception_return we may be
returning to user or kernel context. We already have a test for that,
because we conditionally restore r13. So use that existing test and
branch, and bifurcate the return based on that.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index de276553cc792e300cc107418f3265945ee7a99b..80d90d687d6641c93dac856650c86ed7a7b71760 100644 (file)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -840,7 +840,7 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
        ACCOUNT_CPU_USER_EXIT(r2, r4)
        REST_GPR(13, r1)
-1:
+
        mtspr   SPRN_SRR1,r3
 
        ld      r2,_CCR(r1)
@@ -853,8 +853,22 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
        ld      r3,GPR3(r1)
        ld      r4,GPR4(r1)
        ld      r1,GPR1(r1)
+       RFI_TO_USER
+       b       .       /* prevent speculative execution */
 
-       rfid
+1:     mtspr   SPRN_SRR1,r3
+
+       ld      r2,_CCR(r1)
+       mtcrf   0xFF,r2
+       ld      r2,_NIP(r1)
+       mtspr   SPRN_SRR0,r2
+
+       ld      r0,GPR0(r1)
+       ld      r2,GPR2(r1)
+       ld      r3,GPR3(r1)
+       ld      r4,GPR4(r1)
+       ld      r1,GPR1(r1)
+       RFI_TO_KERNEL
        b       .       /* prevent speculative execution */
 
 #endif /* CONFIG_PPC_BOOK3E */