Reapply "arm64: fpsimd: Implement lazy restore for kernel mode FPSIMD"

commit f481bb32d60e45fb3d19ea68ce79c5629f3fc3a0 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index ce6eebd6c08bdbc7faca37980de6d64f6cb7c3a3..5b0a04810b236b2b1a903547ca3d12f9d32b6675 100644 (file)
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -169,6 +169,7 @@ 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 6e1c935df5c6dbe11a598860b9f3500f5409a6e0..5e7b0eb4687e1cea811028566d9dcec7357e197b 100644 (file)
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1492,12 +1492,30 @@ 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();
 }
 
 /*