This patch provides implementation for the PR_SVE_SET_VL and
PR_SVE_GET_VL prctls, which allow a task to set and query its
vector length and associated control flags (although no flags are
defined in this patch).
Currently any thread can set its VL, allowing a mix of VLs within
a single process -- this behaviour will be refined in susequent
patches.
Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
---
arch/arm64/include/asm/fpsimd.h | 2 ++
arch/arm64/kernel/fpsimd.c | 65 +++++++++++++++++++++++++++++++++++++++--
2 files changed, 65 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 22d09c0..1ec2363 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -103,6 +103,8 @@ extern void sve_save_state(void *state, u32 *pfpsr);
extern void sve_load_state(void const *state, u32 const *pfpsr,
unsigned long vq_minus_1);
extern unsigned int sve_get_vl(void);
+extern int sve_set_vector_length(struct task_struct *task,
+ unsigned long vl, unsigned long flags);
/*
* FPSIMD/SVE synchronisation helpers for ptrace:
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 54d7ed0..5f2c24a 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -493,17 +493,78 @@ void fpsimd_sync_from_fpsimd_zeropad(struct task_struct *task)
__fpsimd_sync_from_fpsimd_zeropad(task, sve_vq_from_vl(vl));
}
+int sve_set_vector_length(struct task_struct *task,
+ unsigned long vl, unsigned long flags)
+{
+ BUG_ON(task == current && preemptible());
+
+ if (flags)
+ return -EINVAL; /* No flags defined yet */
+
+ if (!sve_vl_valid(vl))
+ return -EINVAL;
+
+ if (vl > sve_max_vl) {
+ BUG_ON(!sve_vl_valid(sve_max_vl));
+ vl = sve_max_vl;
+ }
+
+ /*
+ * To ensure the FPSIMD bits of the SVE vector registers are preserved,
+ * write any live register state back to task_struct, and convert to a
+ * non-SVE thread.
+ */
+ if (vl != task->thread.sve_vl) {
+ if (task == current &&
+ !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))
+ task_fpsimd_save(current);
+
+ if (test_and_clear_tsk_thread_flag(task, TIF_SVE))
+ task_sve_to_fpsimd(task);
+
+ /*
+ * To avoid surprises, also zero out the SVE regs storage.
+ * This means that the P-regs, FFR and high bits of Z-regs
+ * will read as zero on next access:
+ */
+ clear_sve_regs(task);
+ }
+
+ task->thread.sve_vl = vl;
+
+ fpsimd_flush_task_state(task);
+
+ return 0;
+}
+
/* PR_SVE_SET_VL */
int sve_set_task_vl(struct task_struct *task,
unsigned long vector_length, unsigned long flags)
{
- return -EINVAL;
+ int ret;
+
+ if (!(elf_hwcap & HWCAP_SVE))
+ return -EINVAL;
+
+ BUG_ON(task != current);
+
+ preempt_disable();
+ ret = sve_set_vector_length(current, vector_length, flags);
+ preempt_enable();
+
+ if (ret)
+ return ret;
+
+ return task->thread.sve_vl;
}
/* PR_SVE_GET_VL */
int sve_get_task_vl(struct task_struct *task)
{
- return -EINVAL;
+ if (!(elf_hwcap & HWCAP_SVE))
+ return -EINVAL;
+
+ return task->thread.sve_vl;
}
#endif /* CONFIG_ARM64_SVE */
--
2.1.4
--
To unsubscribe from this list: send the line "unsubscribe linux-arch" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
