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authorCyril Bur <cyrilbur@gmail.com>2016-09-23 16:18:08 +1000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-10-31 05:02:14 -0600
commit613036d9e91990f2043130ff8f78fd770432b3de (patch)
tree3fe447b46b0d5542bd925f385cd1da044deda130
parentd7baac249b8309948ccfe12ad104fb14982c9692 (diff)
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powerpc: Always restore FPU/VEC/VSX if hardware transactional memory in use
commit dc16b553c949e81f37555777dc7bab66d78285a7 upstream. Comment from arch/powerpc/kernel/process.c:967: If userspace is inside a transaction (whether active or suspended) and FP/VMX/VSX instructions have ever been enabled inside that transaction, then we have to keep them enabled and keep the FP/VMX/VSX state loaded while ever the transaction continues. The reason is that if we didn't, and subsequently got a FP/VMX/VSX unavailable interrupt inside a transaction, we don't know whether it's the same transaction, and thus we don't know which of the checkpointed state and the ransactional state to use. restore_math() restore_fp() and restore_altivec() currently may not restore the registers. It doesn't appear that this is more serious than a performance penalty. If the math registers aren't restored the userspace thread will still be run with the facility disabled. Userspace will not be able to read invalid values. On the first access it will take an facility unavailable exception and the kernel will detected an active transaction, at which point it will abort the transaction. There is the possibility for a pathological case preventing any progress by transactions, however, transactions are never guaranteed to make progress. Fixes: 70fe3d9 ("powerpc: Restore FPU/VEC/VSX if previously used") Signed-off-by: Cyril Bur <cyrilbur@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/powerpc/kernel/process.c21
1 files changed, 18 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 9ee2623e0f67..59ef4417545f 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -88,7 +88,13 @@ static void check_if_tm_restore_required(struct task_struct *tsk)
set_thread_flag(TIF_RESTORE_TM);
}
}
+
+static inline bool msr_tm_active(unsigned long msr)
+{
+ return MSR_TM_ACTIVE(msr);
+}
#else
+static inline bool msr_tm_active(unsigned long msr) { return false; }
static inline void check_if_tm_restore_required(struct task_struct *tsk) { }
#endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
@@ -208,7 +214,7 @@ void enable_kernel_fp(void)
EXPORT_SYMBOL(enable_kernel_fp);
static int restore_fp(struct task_struct *tsk) {
- if (tsk->thread.load_fp) {
+ if (tsk->thread.load_fp || msr_tm_active(tsk->thread.regs->msr)) {
load_fp_state(&current->thread.fp_state);
current->thread.load_fp++;
return 1;
@@ -278,7 +284,8 @@ EXPORT_SYMBOL_GPL(flush_altivec_to_thread);
static int restore_altivec(struct task_struct *tsk)
{
- if (cpu_has_feature(CPU_FTR_ALTIVEC) && tsk->thread.load_vec) {
+ if (cpu_has_feature(CPU_FTR_ALTIVEC) &&
+ (tsk->thread.load_vec || msr_tm_active(tsk->thread.regs->msr))) {
load_vr_state(&tsk->thread.vr_state);
tsk->thread.used_vr = 1;
tsk->thread.load_vec++;
@@ -464,7 +471,8 @@ void restore_math(struct pt_regs *regs)
{
unsigned long msr;
- if (!current->thread.load_fp && !loadvec(current->thread))
+ if (!msr_tm_active(regs->msr) &&
+ !current->thread.load_fp && !loadvec(current->thread))
return;
msr = regs->msr;
@@ -983,6 +991,13 @@ void restore_tm_state(struct pt_regs *regs)
msr_diff = current->thread.ckpt_regs.msr & ~regs->msr;
msr_diff &= MSR_FP | MSR_VEC | MSR_VSX;
+ /* Ensure that restore_math() will restore */
+ if (msr_diff & MSR_FP)
+ current->thread.load_fp = 1;
+#ifdef CONFIG_ALIVEC
+ if (cpu_has_feature(CPU_FTR_ALTIVEC) && msr_diff & MSR_VEC)
+ current->thread.load_vec = 1;
+#endif
restore_math(regs);
regs->msr |= msr_diff;