[RFC PATCH v2 23/41] arm64/sve: Move ZEN handling to the common task_fpsimd_load() path

[Dave Martin]

Currently, ZEN is handled only in fpsimd_restore_current_state(),
which is not sufficient since it applies only in certain
situations.

Since all the relevant paths call task_fpsimd_load(), this patch
moves the ZEN handling there.

Signed-off-by: Dave Martin <Dave.Martin at arm.com>
---
 arch/arm64/include/asm/thread_info.h |  1 +
 arch/arm64/kernel/fpsimd.c           | 50 ++++++++++++++++++++----------------
 2 files changed, 29 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 272c32d..a0f5498 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -107,6 +107,7 @@ struct thread_info {
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
+#define _TIF_SVE		(1 << TIF_SVE)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
 #define _TIF_32BIT		(1 << TIF_32BIT)
 
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 260438d..5fb5585 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -37,6 +37,9 @@
 #define FPEXC_IXF	(1 << 4)
 #define FPEXC_IDF	(1 << 7)
 
+/* Forward declarations for local functions used by both SVE and FPSIMD */
+static void task_fpsimd_load(struct task_struct *task);
+
 /*
  * In order to reduce the number of times the FPSIMD state is needlessly saved
  * and restored, we need to keep track of two things:
@@ -151,18 +154,20 @@ static void sve_to_fpsimd(struct task_struct *task)
 
 void do_sve_acc(unsigned int esr, struct pt_regs *regs)
 {
-	unsigned long tmp;
+	if (test_and_set_thread_flag(TIF_SVE)) {
+		unsigned long tmp;
 
-	if (test_and_set_thread_flag(TIF_SVE))
+		asm ("mrs %0, cpacr_el1" : "=r" (tmp));
+
+		printk(KERN_INFO "%s: Strange, ZEN=%u\n",
+		       __func__, (unsigned int)((tmp >> 16) & 3));
 		BUG();
+	}
 
 	BUG_ON(is_compat_task());
 
 	fpsimd_to_sve(current);
-
-	asm ("mrs %0, cpacr_el1" : "=r" (tmp));
-	asm volatile ("msr cpacr_el1, %0" :: "r" (tmp | (1 << 17)));
-	/* Serialised by exception return to user */
+	task_fpsimd_load(current);
 }
 
 #else /* ! CONFIG_ARM64_SVE */
@@ -220,6 +225,23 @@ static void task_fpsimd_load(struct task_struct *task)
 			       &task->thread.fpsimd_state.fpsr);
 	else
 		fpsimd_load_state(&task->thread.fpsimd_state);
+
+	/*
+	 * Flip SVE enable for userspace if it doesn't match the
+	 * current_task.
+	 */
+	if (IS_ENABLED(CONFIG_ARM64_SVE) && (elf_hwcap & HWCAP_SVE)) {
+		unsigned int tmp, flags;
+
+		asm ("mrs %0, cpacr_el1" : "=r" (tmp));
+		flags = task_thread_info(task)->flags;
+		BUILD_BUG_ON(_TIF_SVE != CPACR_EL1_ZEN_EL0EN);
+		if ((tmp ^ (unsigned long)flags) & _TIF_SVE) {
+			tmp ^= _TIF_SVE;
+			asm volatile ("msr cpacr_el1, %0" :: "r" (tmp));
+			/* Serialised by exception return to user */
+		}
+	}
 }
 
 static void task_fpsimd_save(struct task_struct *task)
@@ -323,27 +345,11 @@ void fpsimd_restore_current_state(void)
 		return;
 	preempt_disable();
 	if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
-		unsigned long tmp;
-		unsigned long flags;
-
 		struct fpsimd_state *st = &current->thread.fpsimd_state;
 
 		task_fpsimd_load(current);
 		this_cpu_write(fpsimd_last_state, st);
 		st->cpu = smp_processor_id();
-
-		if (IS_ENABLED(CONFIG_ARM64_SVE)) {
-			/*
-			 * Flip SVE enable for userspace if it doesn't
-			 * match the current_task.
-			 */
-			asm ("mrs %0, cpacr_el1" : "=r" (tmp));
-			flags = current_thread_info()->flags;
-			if ((tmp ^ (unsigned long)flags) & (1 << 17)) {
-				tmp ^= 1 << 17;
-				asm volatile ("msr cpacr_el1, %0" :: "r" (tmp));
-			}
-		}
 	}
 	preempt_enable();
 }
-- 
2.1.4