Re: [PATCH 12/14] powerpc/64s: system call avoid setting MSR[RI] until we set MSR[EE]

Christophe Leroy [off-list ref] writes:

Le 15/03/2021 à 23:04, Nicholas Piggin a écrit :

quoted

This extends the MSR[RI]=0 window a little further into the system
call in order to pair RI and EE enabling with a single mtmsrd.

Time ago, I proposed to delay that on PPC32 and Michael objected, see 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/9f9dd859d571e324c7412ed9db9da8cfba678257.1548956511.git.christophe.leroy@c-s.fr/

I don't think I objected, I was just curious about what the added
exposure to RI=0 was :)

cheers

quoted

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index bd0c82ac9de5..2f14ac3c377c 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S

@@ -1999,8 +1999,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_REAL_LE)
  	mtctr	r10
  	bctr
  	.else
-	li	r10,MSR_RI
-	mtmsrd 	r10,1			/* Set RI (EE=0) */
  #ifdef CONFIG_RELOCATABLE
  	__LOAD_HANDLER(r10, system_call_common)
  	mtctr	r10

diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index f28f41a1a85a..eef61800f734 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S

@@ -311,10 +311,10 @@ END_BTB_FLUSH_SECTION
  	 * nothing pending. system_call_exception() will call
  	 * trace_hardirqs_off().
  	 */
-	li	r11,IRQS_ALL_DISABLED
-	li	r12,PACA_IRQ_HARD_DIS
+	li	r11,IRQS_DISABLED
+	li	r12,-1 /* Set MSR_EE and MSR_RI */
  	stb	r11,PACAIRQSOFTMASK(r13)
-	stb	r12,PACAIRQHAPPENED(r13)
+	mtmsrd	r12,1
  
  	ENTER_KERNEL_SECURITY_FALLBACK