It's desirable to be able to reset the vector length to some sane
default for new processes, since the new binary and its libraries
processes may or may not be SVE-aware.
This patch tracks the desired post-exec vector length (if any) in a
new thread member sve_vl_onexec, and adds a new thread flag
TIF_SVE_VL_INHERIT to control whether to inherit or reset the
vector length. Currently these are inactive. Subsequent patches
will provide the capability to configure them.
Signed-off-by: Dave Martin <dave.mar...@arm.com>
Cc: Alex Bennée <alex.ben...@linaro.org>
---
Changes since v1
----------------
Requested by Alex Bennée:
* Make sve_vl_onexec an unsigned int: that's the type used virtually
everywhere else, and the memory saving is too minor to be interesting.
---
arch/arm64/include/asm/processor.h | 1 +
arch/arm64/include/asm/thread_info.h | 1 +
arch/arm64/kernel/fpsimd.c | 16 ++++++++++++----
3 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/processor.h
b/arch/arm64/include/asm/processor.h
index 4831d28..3faceac 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -87,6 +87,7 @@ struct thread_struct {
struct fpsimd_state fpsimd_state;
void *sve_state; /* SVE registers, if any */
unsigned int sve_vl; /* SVE vector length */
+ unsigned int sve_vl_onexec; /* SVE vl after next exec */
unsigned long fault_address; /* fault info */
unsigned long fault_code; /* ESR_EL1 value */
struct debug_info debug; /* debugging */
diff --git a/arch/arm64/include/asm/thread_info.h
b/arch/arm64/include/asm/thread_info.h
index f0880fc..d3568ab 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -92,6 +92,7 @@ void arch_setup_new_exec(void);
#define TIF_SINGLESTEP 21
#define TIF_32BIT 22 /* 32bit process */
#define TIF_SVE 23 /* Scalable Vector Extension in
use */
+#define TIF_SVE_VL_INHERIT 24 /* Inherit sve_vl_onexec across exec */
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 9b1ebd7..e20b44d 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -106,6 +106,9 @@
*/
static DEFINE_PER_CPU(struct fpsimd_state *, fpsimd_last_state);
+/* Default VL for tasks that don't set it explicitly: */
+static int sve_default_vl = SVE_VL_MIN;
+
static void sve_free(struct task_struct *task)
{
kfree(task->thread.sve_state);
@@ -380,15 +383,20 @@ void fpsimd_flush_thread(void)
* If a bug causes this to go wrong, we make some noise and
* try to fudge thread.sve_vl to a safe value here.
*/
- vl = current->thread.sve_vl;
-
- if (vl == 0)
- vl = SVE_VL_MIN;
+ vl = current->thread.sve_vl_onexec ?
+ current->thread.sve_vl_onexec : sve_default_vl;
if (WARN_ON(!sve_vl_valid(vl)))
vl = SVE_VL_MIN;
current->thread.sve_vl = vl;
+
+ /*
+ * If the task is not set to inherit, ensure that the vector
+ * length will be reset by a subsequent exec:
+ */
+ if (!test_thread_flag(TIF_SVE_VL_INHERIT))
+ current->thread.sve_vl_onexec = 0;
}
set_thread_flag(TIF_FOREIGN_FPSTATE);
--
2.1.4
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