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

[Liran Alon]

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 <address@hidden> 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 <address@hidden>
> > Signed-off-by: Liran Alon <address@hidden>
> Reviewed-by: Igor Mammedov <address@hidden>
>
> > ---
> >   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);