Re: [PATCH v4] hw/cxl: Add QTG _DSM support for ACPI0017 device

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Fri, 06 Oct 2023 15:15:56 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> Add a simple _DSM call support for the ACPI0017 device to return fake QTG
> ID values of 0 and 1 in all cases. This for _DSM plumbing testing from the OS.
> 
> Following edited for readability
> 
> Device (CXLM)
> {
>     Name (_HID, "ACPI0017")  // _HID: Hardware ID
> ...
>     Method (_DSM, 4, Serialized)  // _DSM: Device-Specific Method
>     {
>         If ((Arg0 == ToUUID ("f365f9a6-a7de-4071-a66a-b40c0b4f8e52")))
>         {
>             If ((Arg2 == Zero))
>             {
>                 Return (Buffer (One) { 0x01 })
>             }
> 
>             If ((Arg2 == One))
>             {
>                 Return (Package (0x02)
>                 {
>                     One,
>                     Package (0x02)
>                     {
>                         Zero,
>                         One
>                     }
>                 })
>             }
>         }
>     }
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> --

You've picked up my bad habit / typo.  Needs to be ---
to stop git picking up this text...

> v4: Change to package of ints rather than buffers. Also moved to 2 QTG IDs
> to improve kernel side testing. Tested on x86 qemu guest against kernel
> QTG ID _DSM parsing code to be upstreamed.
> 
> v3: Fix output assignment to be BE host friendly. Fix typo in comment.
> According to the CXL spec, the DSM output should be 1 WORD to indicate
> the max suppoted QTG ID and a package of 0 or more WORDs for the QTG IDs.
> In this dummy impementation, we have first WORD with a 1 to indcate max
> supprted QTG ID of 1. And second WORD in a package to indicate the QTG
> ID of 0.
> 
> v2: Minor edit to drop reference to switches in patch description.
> Message-Id: <20230904161847.18468-3-Jonathan.Cameron@huawei.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Given it's changed in significant way should drop these.

Anyhow, the tests also need updating.  I can do that and push out
a v5 with tests as well once I've tested.

I'm assuming need tweaked kernel code to test?

> ---
>  hw/acpi/cxl.c         |   69 +++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/i386/acpi-build.c  |    1 +
>  include/hw/acpi/cxl.h |    1 +
>  3 files changed, 71 insertions(+)
> 
> diff --git a/hw/acpi/cxl.c b/hw/acpi/cxl.c
> index 92b46bc9323b..9cd7905ea25a 100644
> --- a/hw/acpi/cxl.c
> +++ b/hw/acpi/cxl.c
> @@ -30,6 +30,75 @@
>  #include "qapi/error.h"
>  #include "qemu/uuid.h"
>  
> +void build_cxl_dsm_method(Aml *dev)
> +{
> +    Aml *method, *ifctx, *ifctx2;
> +
> +    method = aml_method("_DSM", 4, AML_SERIALIZED);
> +    {
> +        Aml *function, *uuid;
> +
> +        uuid = aml_arg(0);
> +        function = aml_arg(2);
> +        /* CXL spec v3.0 9.17.3.1 _DSM Function for Retrieving QTG ID */
> +        ifctx = aml_if(aml_equal(
> +            uuid, aml_touuid("F365F9A6-A7DE-4071-A66A-B40C0B4F8E52")));
> +
> +        /* Function 0, standard DSM query function */
> +        ifctx2 = aml_if(aml_equal(function, aml_int(0)));
> +        {
> +            uint8_t byte_list[1] = { 0x01 }; /* function 1 only */
> +
> +            aml_append(ifctx2,
> +                       aml_return(aml_buffer(sizeof(byte_list), byte_list)));
> +        }
> +        aml_append(ifctx, ifctx2);
> +
> +        /*
> +         * Function 1
> +         * Creating a package with static values. The max supported QTG ID will
> +         * be 1 and recommended QTG IDs are 0 and then 1.
> +         * The values here are statically created to simplify emulation. Values
> +         * from a real BIOS would be determined by the performance of all the
> +         * present CXL memory and then assigned.
> +         */
> +        ifctx2 = aml_if(aml_equal(function, aml_int(1)));
> +        {
> +            Aml *pak, *pak1;
> +
> +            /*
> +             * Return: A package containing two elements - a WORD that returns
> +             * the maximum throttling group that the platform supports, and a
> +             * package containing the QTG ID(s) that the platform recommends.
> +             * Package {
> +             *     Max Supported QTG ID
> +             *     Package {QTG Recommendations}
> +             * }
> +             *
> +             * While the SPEC specified WORD that hints at the value being
> +             * 16bit, the ACPI dump of BIOS DSDT table showed that the values
> +             * are integers with no specific size specification. aml_int() will
> +             * be used for the values.
> +             */
> +            pak1 = aml_package(2);
> +            /* Set QTG ID of 0 */
> +            aml_append(pak1, aml_int(0));
> +            /* Set QTG ID of 1 */
> +            aml_append(pak1, aml_int(1));
> +
> +            pak = aml_package(2);
> +            /* Set Max QTG 1 */
> +            aml_append(pak, aml_int(1));
> +            aml_append(pak, pak1);
> +
> +            aml_append(ifctx2, aml_return(pak));
> +        }
> +        aml_append(ifctx, ifctx2);
> +    }
> +    aml_append(method, ifctx);
> +    aml_append(dev, method);
> +}
> +
>  static void cedt_build_chbs(GArray *table_data, PXBCXLDev *cxl)
>  {
>      PXBDev *pxb = PXB_DEV(cxl);
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 95199c89008a..692af40b1a75 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -1422,6 +1422,7 @@ static void build_acpi0017(Aml *table)
>      method = aml_method("_STA", 0, AML_NOTSERIALIZED);
>      aml_append(method, aml_return(aml_int(0x01)));
>      aml_append(dev, method);
> +    build_cxl_dsm_method(dev);
>  
>      aml_append(scope, dev);
>      aml_append(table, scope);
> diff --git a/include/hw/acpi/cxl.h b/include/hw/acpi/cxl.h
> index acf441888683..8f22c71530d8 100644
> --- a/include/hw/acpi/cxl.h
> +++ b/include/hw/acpi/cxl.h
> @@ -25,5 +25,6 @@ void cxl_build_cedt(GArray *table_offsets, GArray *table_data,
>                      BIOSLinker *linker, const char *oem_id,
>                      const char *oem_table_id, CXLState *cxl_state);
>  void build_cxl_osc_method(Aml *dev);
> +void build_cxl_dsm_method(Aml *dev);
>  
>  #endif
> 
>