On 4/30/24 2:25 PM, Chang S. Bae wrote:
> 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>
> ---
Looks good to me.
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> 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.
Nit: May be helpful to include the section title in 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);
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
