KVM: PPC: elide struct thread_struct instances from stack

Instead of instantiating a whole thread_struct on the stack use only the
required parts of it.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Tested-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 27 insertions, 22 deletions

diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index f6eac2f337d9..801d9f3c70ae 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -1293,12 +1293,17 @@ extern int __kvmppc_vcpu_entry(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);
 int __kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
 {
         int ret;
-        struct thread_struct ext_bkp;
+        double fpr[32][TS_FPRWIDTH];
+        unsigned int fpscr;
+        int fpexc_mode;
 #ifdef CONFIG_ALTIVEC
-        bool save_vec = current->thread.used_vr;
+        vector128 vr[32];
+        vector128 vscr;
+        unsigned long uninitialized_var(vrsave);
+        int used_vr;
 #endif
 #ifdef CONFIG_VSX
-        bool save_vsx = current->thread.used_vsr;
+        int used_vsr;
 #endif
         ulong ext_msr;
 
@@ -1311,27 +1316,27 @@ int __kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
         /* Save FPU state in stack */
         if (current->thread.regs->msr & MSR_FP)
                 giveup_fpu(current);
-        memcpy(ext_bkp.fpr, current->thread.fpr, sizeof(current->thread.fpr));
-        ext_bkp.fpscr = current->thread.fpscr;
-        ext_bkp.fpexc_mode = current->thread.fpexc_mode;
+        memcpy(fpr, current->thread.fpr, sizeof(current->thread.fpr));
+        fpscr = current->thread.fpscr.val;
+        fpexc_mode = current->thread.fpexc_mode;
 
 #ifdef CONFIG_ALTIVEC
         /* Save Altivec state in stack */
-        if (save_vec) {
+        used_vr = current->thread.used_vr;
+        if (used_vr) {
                 if (current->thread.regs->msr & MSR_VEC)
                         giveup_altivec(current);
-                memcpy(ext_bkp.vr, current->thread.vr, sizeof(ext_bkp.vr));
-                ext_bkp.vscr = current->thread.vscr;
-                ext_bkp.vrsave = current->thread.vrsave;
+                memcpy(vr, current->thread.vr, sizeof(current->thread.vr));
+                vscr = current->thread.vscr;
+                vrsave = current->thread.vrsave;
         }
-        ext_bkp.used_vr = current->thread.used_vr;
 #endif
 
 #ifdef CONFIG_VSX
         /* Save VSX state in stack */
-        if (save_vsx && (current->thread.regs->msr & MSR_VSX))
+        used_vsr = current->thread.used_vsr;
+        if (used_vsr && (current->thread.regs->msr & MSR_VSX))
                         __giveup_vsx(current);
-        ext_bkp.used_vsr = current->thread.used_vsr;
 #endif
 
         /* Remember the MSR with disabled extensions */
@@ -1356,22 +1361,22 @@ int __kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
         kvmppc_giveup_ext(vcpu, MSR_VSX);
 
         /* Restore FPU state from stack */
-        memcpy(current->thread.fpr, ext_bkp.fpr, sizeof(ext_bkp.fpr));
-        current->thread.fpscr = ext_bkp.fpscr;
-        current->thread.fpexc_mode = ext_bkp.fpexc_mode;
+        memcpy(current->thread.fpr, fpr, sizeof(current->thread.fpr));
+        current->thread.fpscr.val = fpscr;
+        current->thread.fpexc_mode = fpexc_mode;
 
 #ifdef CONFIG_ALTIVEC
         /* Restore Altivec state from stack */
-        if (save_vec && current->thread.used_vr) {
-                memcpy(current->thread.vr, ext_bkp.vr, sizeof(ext_bkp.vr));
-                current->thread.vscr = ext_bkp.vscr;
-                current->thread.vrsave= ext_bkp.vrsave;
+        if (used_vr && current->thread.used_vr) {
+                memcpy(current->thread.vr, vr, sizeof(current->thread.vr));
+                current->thread.vscr = vscr;
+                current->thread.vrsave = vrsave;
         }
-        current->thread.used_vr = ext_bkp.used_vr;
+        current->thread.used_vr = used_vr;
 #endif
 
 #ifdef CONFIG_VSX
-        current->thread.used_vsr = ext_bkp.used_vsr;
+        current->thread.used_vsr = used_vsr;
 #endif
 
         return ret;