From f481bb32d60e45fb3d19ea68ce79c5629f3fc3a0 Mon Sep 17 00:00:00 2001
From: Will Deacon <will@kernel.org>
Date: Wed, 22 May 2024 11:53:05 +0100
Subject: [PATCH] Reapply "arm64: fpsimd: Implement lazy restore for kernel
mode FPSIMD"
This reverts commit b8995a18417088bb53f87c49d200ec72a9dd4ec1.
Ard managed to reproduce the dm-crypt corruption problem and got to the
bottom of it, so re-apply the problematic patch in preparation for
fixing things properly.
Cc: stable@vger.kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/processor.h | 1 +
arch/arm64/kernel/fpsimd.c | 18 ++++++++++++++++++
2 files changed, 19 insertions(+)
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 4f122b932ccac..f77371232d8c6 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -171,6 +171,7 @@ struct thread_struct {
struct debug_info debug; /* debugging */
struct user_fpsimd_state kernel_fpsimd_state;
+ unsigned int kernel_fpsimd_cpu;
#ifdef CONFIG_ARM64_PTR_AUTH
struct ptrauth_keys_user keys_user;
#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index e9d70dc915117..ebb0158997cab 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1509,12 +1509,30 @@ void do_fpsimd_exc(unsigned long esr, struct pt_regs *regs)
static void fpsimd_load_kernel_state(struct task_struct *task)
{
+ struct cpu_fp_state *last = this_cpu_ptr(&fpsimd_last_state);
+
+ /*
+ * Elide the load if this CPU holds the most recent kernel mode
+ * FPSIMD context of the current task.
+ */
+ if (last->st == &task->thread.kernel_fpsimd_state &&
+ task->thread.kernel_fpsimd_cpu == smp_processor_id())
+ return;
+
fpsimd_load_state(&task->thread.kernel_fpsimd_state);
}
static void fpsimd_save_kernel_state(struct task_struct *task)
{
+ struct cpu_fp_state cpu_fp_state = {
+ .st = &task->thread.kernel_fpsimd_state,
+ .to_save = FP_STATE_FPSIMD,
+ };
+
fpsimd_save_state(&task->thread.kernel_fpsimd_state);
+ fpsimd_bind_state_to_cpu(&cpu_fp_state);
+
+ task->thread.kernel_fpsimd_cpu = smp_processor_id();
}
void fpsimd_thread_switch(struct task_struct *next)
--
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