commit b5b6c6b1f3d9d274428f7e69c8d491caaac3c7d0
Author: Breno Leitao <breno.leitao@gmail.com>
Date:   Wed Jun 21 17:01:33 2017 -0400

    powerpc/kernel: Disassociate FP and VEC laziness

    Currently, if an application only uses FP, then VEC registers will
    continue to be saved and loaded on context switches independently if
    they are being used or not.

    This change disassociate both of them, i.e, stop restoring VEC if it is
    not used. The same thing for FP (if only VEC is being used).

    In order to do so, we are relaying on load_vec and load_fp, if they
    overflow to zero, we stop restoring the registers until an exception
    happens and load_{fp,vec} become positive again.

    Signed-off-by: Breno Leitao <leitao@debian.org>
    Signed-off-by: Gustavo Romero <gromero@linux.vnet.ibm.com>

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 5d6af58270e6..9a4bd01094ef 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -243,8 +243,6 @@ static int restore_fp(struct task_struct *tsk) { return 0; }
 #endif /* CONFIG_PPC_FPU */

 #ifdef CONFIG_ALTIVEC
-#define loadvec(thr) ((thr).load_vec)
-
 static void __giveup_altivec(struct task_struct *tsk)
 {
    unsigned long msr;
@@ -323,7 +321,6 @@ static int restore_altivec(struct task_struct *tsk)
    return 0;
 }
 #else
-#define loadvec(thr) 0
 static inline int restore_altivec(struct task_struct *tsk) { return 0; }
 #endif /* CONFIG_ALTIVEC */

@@ -506,9 +503,16 @@ EXPORT_SYMBOL(giveup_all);
 void restore_math(struct pt_regs *regs)
 {
    unsigned long msr;
+   u8 load_fp = current->thread.load_fp;
+   u8 load_vec = current->thread.load_vec;

-   if (!msr_tm_active(regs->msr) &&
-       !current->thread.load_fp && !loadvec(current->thread))
+   /* If in TM mode, force restore of vec and fp.
+    * If not in TM and !load_vec and !load_fp, return now
+    */
+   if (msr_tm_active(regs->msr)) {
+       load_vec = 1;
+       load_fp = 1;
+   } else if (!load_fp && !load_vec)
        return;

    msr = regs->msr;
@@ -518,10 +522,10 @@ void restore_math(struct pt_regs *regs)
     * Only reload if the bit is not set in the user MSR, the bit BEING set
     * indicates that the registers are hot
     */
-   if ((!(msr & MSR_FP)) && restore_fp(current))
+   if (load_fp && (!(msr & MSR_FP)) && restore_fp(current))
        msr |= MSR_FP | current->thread.fpexc_mode;

-   if ((!(msr & MSR_VEC)) && restore_altivec(current))
+   if (load_vec && (!(msr & MSR_VEC)) && restore_altivec(current))
        msr |= MSR_VEC;

    if ((msr & (MSR_FP | MSR_VEC)) == (MSR_FP | MSR_VEC) &&

commit 4055dd873df463db78461fda8849b4e07076f1ee
Author: Breno Leitao <breno.leitao@gmail.com>
Date:   Wed Jun 21 15:16:42 2017 -0400

    powerpc/kernel: Avoid redundancies on giveup_all

    Currently giveup_all() call __giveup_fpu(), __giveup_altivec() and
    __giveup_vsx(), but, __giveup_vsx() calls __giveup_fpu() and
    __giveup_altivec() again, in a redudant manner.

    Other than giving up FPU and Altivec, __giveup_vsx() also disables
    MSR_VSX on MSR, but this is already done on by __giveup_{fp,altivec}().
    As VSX could not be enabled alone (without FP and/or VEC enabled), this
    is also a redundancy.

    This change improves giveup_all() in just 3%, but since giveup_all() is
    called very frequently, around 8x per CPU per second, this change might
    be interesting.

    Signed-off-by: Breno Leitao <leitao@debian.org>
    Signed-off-by: Gustavo Romero <gromero@linux.vnet.ibm.com>

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 2ad725ef4368..5d6af58270e6 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -494,10 +494,6 @@ void giveup_all(struct task_struct *tsk)
    if (usermsr & MSR_VEC)
        __giveup_altivec(tsk);
 #endif
-#ifdef CONFIG_VSX
-   if (usermsr & MSR_VSX)
-       __giveup_vsx(tsk);
-#endif
 #ifdef CONFIG_SPE
    if (usermsr & MSR_SPE)
        __giveup_spe(tsk);