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

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This reverts commit b8995a1841.

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>
This commit is contained in:
Will Deacon 2024-05-22 11:53:05 +01:00
parent ffbf4fb9b5
commit f481bb32d6
2 changed files with 19 additions and 0 deletions
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1
arch/arm64/include/asm/processor.h
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@ -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

18
arch/arm64/kernel/fpsimd.c
View File

@ -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)