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Re: [PATCH 2/3] acpi/processor: sanitize _PDC buffer bits when running as Xen dom0
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 21 Nov 2022 15:10:36 +0100
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, jgross@xxxxxxxx, stable@xxxxxxxxxxxxxxx, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, x86@xxxxxxxxxx, "H. Peter Anvin" <hpa@xxxxxxxxx>, "Rafael J. Wysocki" <rafael@xxxxxxxxxx>, Len Brown <lenb@xxxxxxxxxx>, linux-acpi@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
- Delivery-date: Mon, 21 Nov 2022 14:10:45 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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
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