powerpc/64s: avoid reloading (H)SRR registers if they are still valid

When an interrupt is taken, the SRR registers are set to return to where
it left off. Unless they are modified in the meantime, or the return
address or MSR are modified, there is no need to reload these registers
when returning from interrupt.

Introduce per-CPU flags that track the validity of SRR and HSRR
registers. These are cleared when returning from interrupt, when
using the registers for something else (e.g., OPAL calls), when
adjusting the return address or MSR of a context, and when context
switching (which changes the return address and MSR).

This improves the performance of interrupt returns.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Fold in fixup patch from Nick]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210617155116.2167984-5-npiggin@gmail.com

1 files changed, 16 insertions, 14 deletions

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 16b41470ec92..1831bba0582e 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -354,7 +354,7 @@ static long notrace __unsafe_restore_sigcontext(struct task_struct *tsk, sigset_
 	/* get MSR separately, transfer the LE bit if doing signal return */
 	unsafe_get_user(msr, &sc->gp_regs[PT_MSR], efault_out);
 	if (sig)
-		regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
+		regs_set_return_msr(regs, (regs->msr & ~MSR_LE) | (msr & MSR_LE));
 	unsafe_get_user(regs->orig_gpr3, &sc->gp_regs[PT_ORIG_R3], efault_out);
 	unsafe_get_user(regs->ctr, &sc->gp_regs[PT_CTR], efault_out);
 	unsafe_get_user(regs->link, &sc->gp_regs[PT_LNK], efault_out);
@@ -376,7 +376,7 @@ static long notrace __unsafe_restore_sigcontext(struct task_struct *tsk, sigset_
 	 * This has to be done before copying stuff into tsk->thread.fpr/vr
 	 * for the reasons explained in the previous comment.
 	 */
-	regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX);
+	regs_set_return_msr(regs, regs->msr & ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX));
 
 #ifdef CONFIG_ALTIVEC
 	unsafe_get_user(v_regs, &sc->v_regs, efault_out);
@@ -468,7 +468,7 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
 		return -EINVAL;
 
 	/* pull in MSR LE from user context */
-	regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
+	regs_set_return_msr(regs, (regs->msr & ~MSR_LE) | (msr & MSR_LE));
 
 	/* The following non-GPR non-FPR non-VR state is also checkpointed: */
 	err |= __get_user(regs->ctr, &tm_sc->gp_regs[PT_CTR]);
@@ -495,7 +495,7 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
 	 * This has to be done before copying stuff into tsk->thread.fpr/vr
 	 * for the reasons explained in the previous comment.
 	 */
-	regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX);
+	regs_set_return_msr(regs, regs->msr & ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX));
 
 #ifdef CONFIG_ALTIVEC
 	err |= __get_user(v_regs, &sc->v_regs);
@@ -565,7 +565,7 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
 	preempt_disable();
 
 	/* pull in MSR TS bits from user context */
-	regs->msr |= msr & MSR_TS_MASK;
+	regs_set_return_msr(regs, regs->msr | (msr & MSR_TS_MASK));
 
 	/*
 	 * Ensure that TM is enabled in regs->msr before we leave the signal
@@ -583,7 +583,7 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
 	 * to be de-scheduled with MSR[TS] set but without calling
 	 * tm_recheckpoint(). This can cause a bug.
 	 */
-	regs->msr |= MSR_TM;
+	regs_set_return_msr(regs, regs->msr | MSR_TM);
 
 	/* This loads the checkpointed FP/VEC state, if used */
 	tm_recheckpoint(&tsk->thread);
@@ -591,11 +591,11 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
 	msr_check_and_set(msr & (MSR_FP | MSR_VEC));
 	if (msr & MSR_FP) {
 		load_fp_state(&tsk->thread.fp_state);
-		regs->msr |= (MSR_FP | tsk->thread.fpexc_mode);
+		regs_set_return_msr(regs, regs->msr | (MSR_FP | tsk->thread.fpexc_mode));
 	}
 	if (msr & MSR_VEC) {
 		load_vr_state(&tsk->thread.vr_state);
-		regs->msr |= MSR_VEC;
+		regs_set_return_msr(regs, regs->msr | MSR_VEC);
 	}
 
 	preempt_enable();
@@ -717,6 +717,7 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
 
 	/* This returns like rt_sigreturn */
 	set_thread_flag(TIF_RESTOREALL);
+
 	return 0;
 
 efault_out:
@@ -783,7 +784,7 @@ SYSCALL_DEFINE0(rt_sigreturn)
 		 * the MSR[TS] that came from user context later, at
 		 * restore_tm_sigcontexts.
 		 */
-		regs->msr &= ~MSR_TS_MASK;
+		regs_set_return_msr(regs, regs->msr & ~MSR_TS_MASK);
 
 		if (__get_user(msr, &uc->uc_mcontext.gp_regs[PT_MSR]))
 			goto badframe;
@@ -815,7 +816,8 @@ SYSCALL_DEFINE0(rt_sigreturn)
 		 * MSR[TS] set, but without CPU in the proper state,
 		 * causing a TM bad thing.
 		 */
-		current->thread.regs->msr &= ~MSR_TS_MASK;
+		regs_set_return_msr(current->thread.regs,
+				current->thread.regs->msr & ~MSR_TS_MASK);
 		if (!user_read_access_begin(&uc->uc_mcontext, sizeof(uc->uc_mcontext)))
 			goto badframe;
 
@@ -829,6 +831,7 @@ SYSCALL_DEFINE0(rt_sigreturn)
 		goto badframe;
 
 	set_thread_flag(TIF_RESTOREALL);
+
 	return 0;
 
 badframe_block:
@@ -908,12 +911,12 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 
 	/* Set up to return from userspace. */
 	if (tsk->mm->context.vdso) {
-		regs->nip = VDSO64_SYMBOL(tsk->mm->context.vdso, sigtramp_rt64);
+		regs_set_return_ip(regs, VDSO64_SYMBOL(tsk->mm->context.vdso, sigtramp_rt64));
 	} else {
 		err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 		if (err)
 			goto badframe;
-		regs->nip = (unsigned long) &frame->tramp[0];
+		regs_set_return_ip(regs, (unsigned long) &frame->tramp[0]);
 	}
 
 	/* Allocate a dummy caller frame for the signal handler. */
@@ -938,8 +941,7 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 	}
 
 	/* enter the signal handler in native-endian mode */
-	regs->msr &= ~MSR_LE;
-	regs->msr |= (MSR_KERNEL & MSR_LE);
+	regs_set_return_msr(regs, (regs->msr & ~MSR_LE) | (MSR_KERNEL & MSR_LE));
 	regs->gpr[1] = newsp;
 	regs->gpr[3] = ksig->sig;
 	regs->result = 0;