Re: [PATCH 14/16] ACPI: Add CXL isolation _OSC fields

["Rafael J. Wysocki" <rafael@kernel.org>]

Cc: Dave

On Wed, Jul 30, 2025 at 11:50 PM Ben Cheatham <Benjamin.Cheatham@amd.com> wrote:
>
> Add CXL Timeout and Isolation _OSC support and control fields, as
> defined in the ECN at the link below. The ECN contents are expected to
> appear in the CXL 4.0 specification. The link is only accessible to CXL
> SSWG members, so a brief overview is provided here:
>
> The ECN adds several fields to the CXL _OSC method (CXL 3.2 9.18.2)
> for the purpose of reserving CXL isolation features for the platform
> firmware's use. The fields introduced for kernel support reserve
> toggling the CXL.mem isolation enable bit in the isolation control
> register (CXL 3.2 8.2.4.24.2) and how the host is notified isolation has
> occurred.
>
> These fields will be used by the CXL driver to enable CXL isolation
> according to the result of the handshake. Descriptions of these fields
> are included in the commit messages of the commits where they are used.
>
> Link: https://members.computeexpresslink.org/wg/software_systems/document/3118
> Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>

In case you need this

Acked-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>

> ---
>  drivers/acpi/pci_root.c | 9 +++++++++
>  include/linux/acpi.h    | 3 +++
>  2 files changed, 12 insertions(+)
>
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 74ade4160314..33a922e160fc 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -145,10 +145,13 @@ static struct pci_osc_bit_struct cxl_osc_support_bit[] = {
>         { OSC_CXL_2_0_PORT_DEV_REG_ACCESS_SUPPORT, "CXL20PortDevRegAccess" },
>         { OSC_CXL_PROTOCOL_ERR_REPORTING_SUPPORT, "CXLProtocolErrorReporting" },
>         { OSC_CXL_NATIVE_HP_SUPPORT, "CXLNativeHotPlug" },
> +       { OSC_CXL_TIMEOUT_ISOLATION_SUPPORT, "CXLTimeoutIsolation" },
>  };
>
>  static struct pci_osc_bit_struct cxl_osc_control_bit[] = {
>         { OSC_CXL_ERROR_REPORTING_CONTROL, "CXLMemErrorReporting" },
> +       { OSC_CXL_MEM_ISOLATION_CONTROL, "CXLMemIsolation" },
> +       { OSC_CXL_ISOLATION_NOTIF_CONTROL, "CXLIsolationNotifications" },
>  };
>
>  static void decode_osc_bits(struct acpi_pci_root *root, char *msg, u32 word,
> @@ -493,6 +496,8 @@ static u32 calculate_cxl_support(void)
>                 support |= OSC_CXL_PROTOCOL_ERR_REPORTING_SUPPORT;
>         if (IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE))
>                 support |= OSC_CXL_NATIVE_HP_SUPPORT;
> +       if (IS_ENABLED(CONFIG_CXL_ISOLATION))
> +               support |= OSC_CXL_TIMEOUT_ISOLATION_SUPPORT;
>
>         return support;
>  }
> @@ -535,6 +540,10 @@ static u32 calculate_cxl_control(void)
>         if (IS_ENABLED(CONFIG_MEMORY_FAILURE))
>                 control |= OSC_CXL_ERROR_REPORTING_CONTROL;
>
> +       if (IS_ENABLED(CONFIG_CXL_ISOLATION))
> +               control |= (OSC_CXL_MEM_ISOLATION_CONTROL |
> +                           OSC_CXL_ISOLATION_NOTIF_CONTROL);
> +
>         return control;
>  }
>
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index f102c0fe3431..f172182aa029 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -626,9 +626,12 @@ extern u32 osc_sb_native_usb4_control;
>  #define OSC_CXL_2_0_PORT_DEV_REG_ACCESS_SUPPORT        0x00000002
>  #define OSC_CXL_PROTOCOL_ERR_REPORTING_SUPPORT 0x00000004
>  #define OSC_CXL_NATIVE_HP_SUPPORT              0x00000008
> +#define OSC_CXL_TIMEOUT_ISOLATION_SUPPORT      0x00000010
>
>  /* CXL _OSC: Capabilities DWORD 5: Control Field */
>  #define OSC_CXL_ERROR_REPORTING_CONTROL                0x00000001
> +#define OSC_CXL_MEM_ISOLATION_CONTROL          0x00000002
> +#define OSC_CXL_ISOLATION_NOTIF_CONTROL                0x00000020
>
>  static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
>  {
> --