Re: [RFC PATCH v2 2/4] acpi: fadt: support revision 6.0 of the ACPI specification

[Miguel Luis]

> On 11 Oct 2022, at 05:02, Ani Sinha <ani@anisinha.ca> wrote:
> 
> On Mon, Oct 10, 2022 at 6:53 PM Miguel Luis <miguel.luis@oracle.com> wrote:
>> 
>> Update the Fixed ACPI Description Table (FADT) to revision 6.0 of the ACPI
>> specification adding the field "Hypervisor Vendor Identity" that was missing.
>> 
>> This field's description states the following: "64-bit identifier of 
>> hypervisor
>> vendor. All bytes in this field are considered part of the vendor identity.
>> These identifiers are defined independently by the vendors themselves,
>> usually following the name of the hypervisor product. Version information
>> should NOT be included in this field - this shall simply denote the vendor's
>> name or identifier. Version information can be communicated through a
>> supplemental vendor-specific hypervisor API. Firmware implementers would
>> place zero bytes into this field, denoting that no hypervisor is present in
>> the actual firmware."
>> 
>> Hereupon, what should a valid identifier of an Hypervisor Vendor ID be and
>> where should QEMU provide that information?
>> 
>> On the v1 [1] of this RFC there's the suggestion of having this information
>> in sync by the current acceleration name. This also seems to imply that QEMU,
>> which generates the FADT table, and the FADT consumer need to be in sync with
>> the values of this field.
>> 
>> This version follows Ani Sinha's suggestion [2] of using "QEMU" for the
>> hypervisor vendor ID.
>> 
>> [1]: https://lists.nongnu.org/archive/html/qemu-devel/2022-10/msg00911.html
>> [2]: https://lists.nongnu.org/archive/html/qemu-devel/2022-10/msg00989.html
>> 
>> Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
> 
> Reviewed-by: Ani Sinha <ani@anisinha.ca>
> 

Thank you Ani. In the meanwhile, taking the description part of: “Firmware
implementers would place zero bytes into this field, denoting that no
hypervisor is present in the actual firmware.", I reached to something along
the lines below:

diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
index 42feb4d4d7..e719afe0cb 100644
--- a/hw/acpi/aml-build.c
+++ b/hw/acpi/aml-build.c
@@ -2198,7 +2198,11 @@ void build_fadt(GArray *tbl, BIOSLinker *linker, const 
AcpiFadtData *f,
     }
 
     /* Hypervisor Vendor Identity */
-    build_append_padded_str(tbl, "QEMU", 8, '\0');
+    if (f->hyp_is_present) {
+        build_append_padded_str(tbl, "QEMU", 8, '\0');
+    } else {
+        build_append_int_noprefix(tbl, 0, 8);
+    }
 
     /* TODO: extra fields need to be added to support revisions above rev6 */
     assert(f->rev == 6);
diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index 72bb6f61a5..d238ce2b88 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -818,6 +818,7 @@ static void build_fadt_rev6(GArray *table_data, BIOSLinker 
*linker,
         .minor_ver = 0,
         .flags = 1 << ACPI_FADT_F_HW_REDUCED_ACPI,
         .xdsdt_tbl_offset = &dsdt_tbl_offset,
+        .hyp_is_present = vms->virt && (kvm_enabled() || hvf_enabled()),
     };
 
     switch (vms->psci_conduit) {
diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h
index 2b42e4192b..2aff5304af 100644
--- a/include/hw/acpi/acpi-defs.h
+++ b/include/hw/acpi/acpi-defs.h
@@ -79,7 +79,7 @@ typedef struct AcpiFadtData {
     uint16_t arm_boot_arch;    /* ARM_BOOT_ARCH */
     uint16_t iapc_boot_arch;   /* IAPC_BOOT_ARCH */
     uint8_t minor_ver;         /* FADT Minor Version */
-
+    bool hyp_is_present;
     /*
      * respective tables offsets within ACPI_BUILD_TABLE_FILE,
      * NULL if table doesn't exist (in that case field's value

Any thoughts on this?

Thanks
Miguel

>> ---
>> hw/acpi/aml-build.c      | 13 ++++++++++---
>> hw/arm/virt-acpi-build.c | 10 +++++-----
>> 2 files changed, 15 insertions(+), 8 deletions(-)
>> 
>> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
>> index e6bfac95c7..42feb4d4d7 100644
>> --- a/hw/acpi/aml-build.c
>> +++ b/hw/acpi/aml-build.c
>> @@ -2070,7 +2070,7 @@ void build_pptt(GArray *table_data, BIOSLinker 
>> *linker, MachineState *ms,
>>     acpi_table_end(linker, &table);
>> }
>> 
>> -/* build rev1/rev3/rev5.1 FADT */
>> +/* build rev1/rev3/rev5.1/rev6.0 FADT */
>> void build_fadt(GArray *tbl, BIOSLinker *linker, const AcpiFadtData *f,
>>                 const char *oem_id, const char *oem_table_id)
>> {
>> @@ -2193,8 +2193,15 @@ void build_fadt(GArray *tbl, BIOSLinker *linker, 
>> const AcpiFadtData *f,
>>     /* SLEEP_STATUS_REG */
>>     build_append_gas_from_struct(tbl, &f->sleep_sts);
>> 
>> -    /* TODO: extra fields need to be added to support revisions above rev5 
>> */
>> -    assert(f->rev == 5);
>> +    if (f->rev == 5) {
>> +        goto done;
>> +    }
>> +
>> +    /* Hypervisor Vendor Identity */
>> +    build_append_padded_str(tbl, "QEMU", 8, '\0');
>> +
>> +    /* TODO: extra fields need to be added to support revisions above rev6 
>> */
>> +    assert(f->rev == 6);
>> 
>> done:
>>     acpi_table_end(linker, &table);
>> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>> index 9b3aee01bf..72bb6f61a5 100644
>> --- a/hw/arm/virt-acpi-build.c
>> +++ b/hw/arm/virt-acpi-build.c
>> @@ -809,13 +809,13 @@ build_madt(GArray *table_data, BIOSLinker *linker, 
>> VirtMachineState *vms)
>> }
>> 
>> /* FADT */
>> -static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
>> +static void build_fadt_rev6(GArray *table_data, BIOSLinker *linker,
>>                             VirtMachineState *vms, unsigned dsdt_tbl_offset)
>> {
>> -    /* ACPI v5.1 */
>> +    /* ACPI v6.0 */
>>     AcpiFadtData fadt = {
>> -        .rev = 5,
>> -        .minor_ver = 1,
>> +        .rev = 6,
>> +        .minor_ver = 0,
>>         .flags = 1 << ACPI_FADT_F_HW_REDUCED_ACPI,
>>         .xdsdt_tbl_offset = &dsdt_tbl_offset,
>>     };
>> @@ -945,7 +945,7 @@ void virt_acpi_build(VirtMachineState *vms, 
>> AcpiBuildTables *tables)
>> 
>>     /* FADT MADT PPTT GTDT MCFG SPCR DBG2 pointed to by RSDT */
>>     acpi_add_table(table_offsets, tables_blob);
>> -    build_fadt_rev5(tables_blob, tables->linker, vms, dsdt);
>> +    build_fadt_rev6(tables_blob, tables->linker, vms, dsdt);
>> 
>>     acpi_add_table(table_offsets, tables_blob);
>>     build_madt(tables_blob, tables->linker, vms);
>> --
>> 2.37.3
>>