From b2b46304e9360f3dda49c9d8ba4a1478b9eecf1d Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Wed, 24 Jun 2020 09:41:39 +1000
Subject: [PATCH] powerpc: re-initialise lazy FPU/VEC counters on every fault
References: jsc#SLE-9246
Patch-mainline: v5.9-rc1
Git-commit: b2b46304e9360f3dda49c9d8ba4a1478b9eecf1d
When a FP/VEC/VSX unavailable fault loads registers and enables the
facility in the MSR, re-set the lazy restore counters to 1 rather
than incrementing them so every fault gets the same number of
restores before the next fault.
This probably shouldn't be a practical change because if a lazy counter
was non-zero then it should have been restored and would not cause a
fault when userspace tries to access it. However the code and comment
implies otherwise so that's misleading and unnecessary.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200623234139.2262227-3-npiggin@gmail.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/kernel/fpu.S | 4 +---
arch/powerpc/kernel/vector.S | 4 +---
2 files changed, 2 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/fpu.S b/arch/powerpc/kernel/fpu.S
index cac22cb97a8c..4ae39db70044 100644
--- a/arch/powerpc/kernel/fpu.S
+++ b/arch/powerpc/kernel/fpu.S
@@ -107,9 +107,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_VSX)
or r12,r12,r4
std r12,_MSR(r1)
#endif
- /* Don't care if r4 overflows, this is desired behaviour */
- lbz r4,THREAD_LOAD_FP(r5)
- addi r4,r4,1
+ li r4,1
stb r4,THREAD_LOAD_FP(r5)
addi r10,r5,THREAD_FPSTATE
lfd fr0,FPSTATE_FPSCR(r10)
diff --git a/arch/powerpc/kernel/vector.S b/arch/powerpc/kernel/vector.S
index efc5b52f95d2..801dc28fdcca 100644
--- a/arch/powerpc/kernel/vector.S
+++ b/arch/powerpc/kernel/vector.S
@@ -76,9 +76,7 @@ _GLOBAL(load_up_altivec)
oris r12,r12,MSR_VEC@h
std r12,_MSR(r1)
#endif
- /* Don't care if r4 overflows, this is desired behaviour */
- lbz r4,THREAD_LOAD_VEC(r5)
- addi r4,r4,1
+ li r4,1
stb r4,THREAD_LOAD_VEC(r5)
addi r6,r5,THREAD_VRSTATE
li r4,1
--
2.28.0