Re: [PATCH 2/3] acpi/processor: sanitize _PDC buffer bits when running as Xen dom0

On 21.11.2022 11:21, Roger Pau Monne wrote:

--- a/drivers/acpi/processor_pdc.c +++ b/drivers/acpi/processor_pdc.c @@ -137,6 +137,14 @@ acpi_processor_eval_pdc(acpi_handle handle, struct acpi_object_list *pdc_in) buffer[2] &= ~(ACPI_PDC_C_C2C3_FFH | ACPI_PDC_C_C1_FFH); }

• if (xen_initial_domain())

• /*
  

•  * When Linux is running as Xen dom0 it's the hypervisor the
  

•  * entity in charge of the processor power management, and so
  

•  * Xen needs to check the OS capabilities reported in the _PDC
  

•  * buffer matches what the hypervisor driver supports.
  

•  */
  

• xen_sanitize_pdc((uint32_t *)pdc_in->pointer->buffer.pointer);
  

  status = acpi_evaluate_object(handle, "_PDC", pdc_in, NULL);

Again looking at our old XenoLinux forward port we had this inside the earlier if(), as an _alternative_ to the &= (I don't think it's valid to apply both the kernel's and Xen's adjustments). That would also let you use "buffer" rather than re-calculating it via yet another (risky from an abstract pov) cast.

It was the very nature of requiring Xen-specific conditionals which I understand was the reason why so far no attempt was made to get this (incl the corresponding logic for patch 1) into any upstream kernel.

Jan