linux-kernel - [RFC PATCH v7 20/21] riscv: Allocate space for vector registers in start

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Date:   Thu, 10 Sep 2020 16:12:15 +0800
From:   Greentime Hu <greentime.hu@...ive.com>
To:     greentime.hu@...ive.com, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, aou@...s.berkeley.edu,
        palmer@...belt.com, paul.walmsley@...ive.com
Cc:     Vincent Chen <vincent.chen@...ive.com>
Subject: [RFC PATCH v7 20/21] riscv: Allocate space for vector registers in start_thread()

It allocates memory space for vector registers in start_thread() instead of
allocating in vstate_restore() in this patch. We can allocate memory here
so that it will be more readable.

Signed-off-by: Greentime Hu <greentime.hu@...ive.com>
Signed-off-by: Vincent Chen <vincent.chen@...ive.com>
---
 arch/riscv/include/asm/switch_to.h | 7 +------
 arch/riscv/kernel/process.c        | 8 ++++++++
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index d33a86a48f0d..58898d33bf28 100644
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -98,12 +98,6 @@ static inline void vstate_restore(struct task_struct *task,
 {
 	if ((regs->status & SR_VS) != SR_VS_OFF) {
 		struct __riscv_v_state *vstate = &(task->thread.vstate);
-
-		/* Allocate space for vector registers. */
-		if (!vstate->datap) {
-			vstate->datap = kzalloc(riscv_vsize, GFP_ATOMIC);
-			vstate->size = riscv_vsize;
-		}
 		__vstate_restore(vstate, vstate->datap);
 		__vstate_clean(regs);
 	}
@@ -122,6 +116,7 @@ static inline void __switch_to_vector(struct task_struct *prev,
 
 #else
 #define has_vector false
+#define riscv_vsize (0)
 #define vstate_save(task, regs) do { } while (0)
 #define vstate_restore(task, regs) do { } while (0)
 #define __switch_to_vector(__prev, __next) do { } while (0)
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index fb485c9bceee..009ab4849fce 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -84,7 +84,15 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
 	}
 
 	if (has_vector) {
+		struct __riscv_v_state *vstate = &(current->thread.vstate);
+
+		/* Enable vector and allocate memory for vector registers. */
+		vstate->datap = kzalloc(riscv_vsize, GFP_KERNEL);
+		if (WARN_ON(!vstate->datap))
+			return;
+		vstate->size = riscv_vsize;
 		regs->status |= SR_VS_INITIAL;
+
 		/*
 		 * Restore the initial value to the vector register
 		 * before starting the user program.
-- 
2.28.0