Re: [PATCH v2 2/3] acpi: Add Windows ACPI Emulated Device Table (WAET)

[Liran Alon <liran.alon@oracle.com>]

As almost two weeks have passed since this Reviewed-By comment, can I 
assume this series is done from my perspective and ready to be merged?
As I haven't seen a Reviewed-By for the rest of the patches of this series.

Thanks,
-Liran

On 16/03/2020 12:28, Igor Mammedov wrote:
> On Fri, 13 Mar 2020 16:50:08 +0200
> Liran Alon <liran.alon@oracle.com> wrote:
>
>> Microsoft introduced this ACPI table to avoid Windows guests performing
>> various workarounds for device erratas. As the virtual device emulated
>> by VMM may not have the errata.
>>
>> Currently, WAET allows hypervisor to inform guest about two
>> specific behaviors: One for RTC and the other for ACPI PM timer.
>>
>> Support for WAET have been introduced since Windows Vista. This ACPI
>> table is also exposed by other common hypervisors by default, including:
>> VMware, GCP and AWS.
>>
>> This patch adds WAET ACPI Table to QEMU.
>>
>> We set "ACPI PM timer good" bit in "Emualted Device Flags" field to
>> indicate that the ACPI PM timer has been enhanced to not require
>> multiple reads to obtain a reliable value.
>> This results in improving the performance of Windows guests that use
>> ACPI PM timer by avoiding unnecessary VMExits caused by these multiple
>> reads.
>>
>> Co-developed-by: Elad Gabay <elad.gabay@oracle.com>
>> Signed-off-by: Liran Alon <liran.alon@oracle.com>
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>
>
>> ---
>>   hw/i386/acpi-build.c | 31 +++++++++++++++++++++++++++++++
>>   1 file changed, 31 insertions(+)
>>
>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>> index 9c4e46fa7466..1c3a2e8fcb3c 100644
>> --- a/hw/i386/acpi-build.c
>> +++ b/hw/i386/acpi-build.c
>> @@ -2512,6 +2512,34 @@ build_dmar_q35(GArray *table_data, BIOSLinker *linker)
>>       build_header(linker, table_data, (void *)(table_data->data + dmar_start),
>>                    "DMAR", table_data->len - dmar_start, 1, NULL, NULL);
>>   }
>> +
>> +/*
>> + * Windows ACPI Emulated Devices Table
>> + * (Version 1.0 - April 6, 2009)
>> + * Spec: https://urldefense.com/v3/__http://download.microsoft.com/download/7/E/7/7E7662CF-CBEA-470B-A97E-CE7CE0D98DC2/WAET.docx__;!!GqivPVa7Brio!MpZ69-947P6dY4Rnd8Cvj0z_9yJ1QdS-SED39RJ5JvT7Rry_rwDpcLlUDJ_ZU7U$
>> + *
>> + * Helpful to speedup Windows guests and ignored by others.
>> + */
>> +static void
>> +build_waet(GArray *table_data, BIOSLinker *linker)
>> +{
>> +    int waet_start = table_data->len;
>> +
>> +    /* WAET header */
>> +    acpi_data_push(table_data, sizeof(AcpiTableHeader));
>> +    /*
>> +     * Set "ACPI PM timer good" flag.
>> +     *
>> +     * Tells Windows guests that our ACPI PM timer is reliable in the
>> +     * sense that guest can read it only once to obtain a reliable value.
>> +     * Which avoids costly VMExits caused by guest re-reading it unnecessarily.
>> +     */
>> +    build_append_int_noprefix(table_data, 1 << 1 /* ACPI PM timer good */, 4);
> this should work but, I'd use (1UL << 1) if you'll need to respin
>
>
>> +
>> +    build_header(linker, table_data, (void *)(table_data->data + waet_start),
>> +                 "WAET", table_data->len - waet_start, 1, NULL, NULL);
>> +}
>> +
>>   /*
>>    *   IVRS table as specified in AMD IOMMU Specification v2.62, Section 5.2
>>    *   accessible here https://urldefense.com/v3/__http://support.amd.com/TechDocs/48882_IOMMU.pdf__;!!GqivPVa7Brio!MpZ69-947P6dY4Rnd8Cvj0z_9yJ1QdS-SED39RJ5JvT7Rry_rwDpcLlUNZTUAnw$
>> @@ -2859,6 +2887,9 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine)
>>                             machine->nvdimms_state, machine->ram_slots);
>>       }
>>   
>> +    acpi_add_table(table_offsets, tables_blob);
>> +    build_waet(tables_blob, tables->linker);
>> +
>>       /* Add tables supplied by user (if any) */
>>       for (u = acpi_table_first(); u; u = acpi_table_next(u)) {
>>           unsigned len = acpi_table_len(u);