The scan test does not start when the AMX state remains active and is not
re-initialized. With the extension of kernel_fpu_begin_mask(), the driver
code can now initialize the state properly.
Introduce custom FPU handling wrappers to ensure compliant with the
established FPU API semantics, as kernel_fpu_begin() exclusively sets
legacy states. This follows the EFI case from commit b0dc553cfc9d
("x86/fpu: Make the EFI FPU calling convention explicit").
Then, use these wrappers to surround the MSR_ACTIVATE_SCAN write to
minimize the critical section. To prevent unnecessary delays, invoke
ifs_fpu_begin() before entering the rendezvous loop.
Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx>
Reviewed-by: Jithu Joseph <jithu.joseph@xxxxxxxxx>
Tested-by: Jithu Joseph <jithu.joseph@xxxxxxxxx>
---
drivers/platform/x86/intel/ifs/ifs.h | 14 ++++++++++++++
drivers/platform/x86/intel/ifs/runtest.c | 6 ++++++
2 files changed, 20 insertions(+)
diff --git a/drivers/platform/x86/intel/ifs/ifs.h b/drivers/platform/x86/intel/ifs/ifs.h
index 56b9f3e3cf76..71d8b50854b2 100644
--- a/drivers/platform/x86/intel/ifs/ifs.h
+++ b/drivers/platform/x86/intel/ifs/ifs.h
@@ -325,4 +325,18 @@ int do_core_test(int cpu, struct device *dev);
extern struct attribute *plat_ifs_attrs[];
extern struct attribute *plat_ifs_array_attrs[];
+static inline void ifs_fpu_begin(void)
+{
+ /*
+ * The AMX state must be initialized prior to executing In-Field
+ * Scan tests, according to Intel SDM.
+ */
+ kernel_fpu_begin_mask(KFPU_AMX);
+}
+
+static inline void ifs_fpu_end(void)
+{
+ kernel_fpu_end();
+}
+
#endif
diff --git a/drivers/platform/x86/intel/ifs/runtest.c b/drivers/platform/x86/intel/ifs/runtest.c
index 95b4b71fab53..a35eac7c0b44 100644
--- a/drivers/platform/x86/intel/ifs/runtest.c
+++ b/drivers/platform/x86/intel/ifs/runtest.c
@@ -188,6 +188,9 @@ static int doscan(void *data)
/* Only the first logical CPU on a core reports result */
first = cpumask_first(cpu_smt_mask(cpu));
+ /* Prepare FPU state before entering the rendezvous loop*/
+ ifs_fpu_begin();
+
wait_for_sibling_cpu(&scan_cpus_in, NSEC_PER_SEC);
/*
@@ -199,6 +202,9 @@ static int doscan(void *data)
* are processed in a single pass) before it retires.
*/
wrmsrl(MSR_ACTIVATE_SCAN, params->activate->data);
+
+ ifs_fpu_end();
+
rdmsrl(MSR_SCAN_STATUS, status.data);
trace_ifs_status(ifsd->cur_batch, start, stop, status.data);
--
2.34.1
