Re: [Qemu-devel] [PATCH v4 1/9] ACPI: Add a function for building named qword entries

[Laszlo Ersek]

On 01/26/17 06:35, Ben Warren wrote:
> 
>> On Jan 25, 2017, at 4:48 PM, Laszlo Ersek <address@hidden
>> <mailto:address@hidden>> wrote:
>>
>> On 01/25/17 19:35, Michael S. Tsirkin wrote:
>>> On Wed, Jan 25, 2017 at 09:36:52AM -0800, Ben Warren wrote:
>>>> Hi Laszlo,
>>>>
>>>>
>>>>    On Jan 24, 2017, at 7:55 PM, Laszlo Ersek <address@hidden
>>>> <mailto:address@hidden>> wrote:
>>>>
>>>>    Hi Ben,
>>>>
>>>>    sorry about being late to reviewing this series. I hope I can now
>>>> spend
>>>>    more time on it.
>>>>
>>>>    - Please do not try to address my comments immediately. It's very
>>>>    possible (even likely) that Igor, MST and myself could have different
>>>>    opinions on things, so first please await agreement between your
>>>> reviewers.
>>>>
>>>>
>>>> Thanks for the very detailed review.  I’ll give it a couple of days
>>>> and then
>>>> start work on the suggested changes.
>>>>
>>>>
>>>>    - I think you should have CC'd Igor and Michael directly. I'm adding
>>>>    them to this reply; hopefully that will be enough for them to monitor
>>>>    this series.
>>>>
>>>>    - I'll likely be unable to review everything with 100% coverage; so
>>>>    addressing (or sufficiently refuting) my comments might not guarantee
>>>>    that the next version will be merged at once.
>>>>
>>>>    With all that said:
>>>>
>>>>    On 01/25/17 02:43, address@hidden
>>>> <mailto:address@hidden> wrote:
>>>>
>>>>        From: Ben Warren <address@hidden
>>>> <mailto:address@hidden>>
>>>>
>>>>        This is initially used to patch a 64-bit address into the VM
>>>> Generation
>>>>        ID SSDT
>>>>
>>>>
>>>>    (1) I think this commit message line is overlong; I think we wrap
>>>> at 74
>>>>    chars or so. Not critical, but worth mentioning.
>>>>
>>>>
>>>>
>>>>        Signed-off-by: Ben Warren <address@hidden
>>>> <mailto:address@hidden>>
>>>>        ---
>>>>        hw/acpi/aml-build.c         | 28 ++++++++++++++++++++++++++++
>>>>        include/hw/acpi/aml-build.h |  4 ++++
>>>>        2 files changed, 32 insertions(+)
>>>>
>>>>        diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
>>>>        index b2a1e40..dc4edc2 100644
>>>>        --- a/hw/acpi/aml-build.c
>>>>        +++ b/hw/acpi/aml-build.c
>>>>        @@ -285,6 +285,34 @@ build_append_named_dword(GArray *array,
>>>> const char
>>>>        *name_format, ...)
>>>>            return offset;
>>>>        }
>>>>
>>>>        +/*
>>>>        + * Build NAME(XXXX, 0x00000000) where 0x00000000 is encoded as a
>>>>        qword,
>>>>        + * and return the offset to 0x00000000 for runtime patching.
>>>>        + *
>>>>        + * Warning: runtime patching is best avoided. Only use this as
>>>>        + * a replacement for DataTableRegion (for guests that don't
>>>>        + * support it).
>>>>        + */
>>>
>>> only one comment: QWords first appeared in ACPI 2.0 and
>>> XP does not like them. Not strictly a blocker as people can
>>> avoid using the feature, but nice to have.
>>
>> Does XP have a driver for VMGENID?
>>
>> If not, then I'd prefer to stick with the qword VGIA.
>>
>>> Will either UEFI or seabios allocate
>>> memory outside 4G range? If not you do not need a qword.
>>
>> Good point (assuming XP has a driver for VMGENID).
>>
>> OVMF keeps all such allocations (i.e., for COMMAND_ALLOCATE and the
>> upcoming COMMAND_ALLOCATE_RETURN_ADDR) under 4GB, so as far as OVMF is
>> concerned, using a dword for the VGIA named object should be fine.
>> Accordingly, a 4-byte wide ADD_POINTER command should be used for
>> patching VGIA.
>>
>> Considering the fw_cfg file that receives the address, and
>> COMMAND_ALLOCATE_RETURN_ADDR more generally, I'd still prefer if those
>> stayed 8-byte wide, regardless of XP's support for VMGENID.
>>
>>
>> Hm... It looks like VMGENID *can* be consumed on Windows XP SP3, as long
>> as "Hyper-V integration services" are installed:
>>
>> https://msdn.microsoft.com/en-us/library/jj643357(v=vs.85).aspx
>>
>>    The virtual machine must be running a guest operating system that
>>    has support for the virtual machine generation identifier.
>>    Currently, these are the following.
>>    The following operating systems have native support for the virtual
>>    machine generation identifier.
>>      [...]
>>
>>    The following operating can be used as the guest operating system
>>    if the Hyper-V integration services from Windows 8 or Windows
>>    Server 2012 are installed.
>>
>>      [...]
>>      * Windows XP with Service Pack 3 (SP3)
>>
>> Additionally, under
>> <https://technet.microsoft.com/en-us/library/dn792027(v=ws.11).aspx>:
>>
>>    Supported Windows client guest operating systems
>>
>>    Windows XP with       [...] Install the integration  [...]
>>    Service Pack 3 (SP3)        services after you set
>>                                up the operating system
>>                                in the virtual machine.
>>
>> This seems to be consistent with the VMGENID spec requirement that the
>> ADDR method return a package of two 32-bit integers, not a single 64-bit
>> one.
>>
>> So, I agree with using a dword for VGIA (and a matching 4-byte wide
>> ADD_POINTER command).
>>
>> But, again, I'd like to keep COMMAND_ALLOCATE_RETURN_ADDR 8-byte wide.
>> In the future we might introduce more allocation hints (for the "zone"
>> field) that would enable the firmware to allocate from the full 64-bit
>> address space.
>>
>> NB, I didn't check SeaBIOS (should be easy for Ben); AFAIR it only uses
>> 16-bit and 32-bit modes.
>>
> Right, it appears that the allocated address will always fit in 32 bits.
>  As mentioned, XP should be OK since the ADDR method returns a package
> of two 32-bit numbers.
> 
> I propose to still include this patch but touch up the comments as
> requested by Laszlo.  This way it will be in the toolbox for future
> users and has been tested.  I will also change VGIA to dword and hard
> code the AML to return ADDR[1] = 0.  

Sounds good!

> 
> FYI: here’s an iasl dump from Windows 2012 Hyper-V in case you haven’t
> seen it.  Note that Microsoft uses E00 and violates the HID name length
> spec:

:)

Thanks!
Laszlo

> Scope (\_SB)
>    {
>        Device (GENC)
>        {
>            Name (_CID, "VM_Gen_Counter")  // _CID: Compatible ID
>            Name (_HID, "Hyper_V_Gen_Counter_V1")  // _HID: Hardware ID
>            Name (_UID, 0x00)  // _UID: Unique ID
>            Name (_DDN, "VM_Gen_Counter")  // _DDN: DOS Device Name
>            Method (ADDR, 0, NotSerialized)
>            {
>                Name (LPKG, Package (0x02)
>                {
>                    0x00, 
>                    0x00
>                })
>                LPKG [0x00] = GCAL /* \GCAL */
>                LPKG [0x01] = GCAH /* \GCAH */
>                Return (LPKG) /* \_SB_.GENC.ADDR.LPKG */
>            }
>        }
>    }
> 
>    Scope (\_GPE)
>    {
>        Method (_E00, 0, NotSerialized)  // _Exx: Edge-Triggered GPE
>        {
>            Notify (\_SB.GENC, 0x80) // Status Change
>        }
>    }
> 
>> Thanks!
>> Laszlo
>>
>>>
>>>
>>>
>>>
>>>>
>>>>    (2) Since we're adding a qword (8-byte integer), the hexadecimal
>>>>    constant should have 16 nibbles: 0x0000000000000000. (After
>>>> copying the
>>>>    comment from build_append_named_dword(), it should be actualized.)
>>>>
>>>>    (3) Normally the functions in this file that create AML operators
>>>> carry
>>>>    a note about the ACPI spec version and exact location that
>>>> defines the
>>>>    operator. I see that commit f20354910893 ("acpi: add
>>>>    build_append_named_dword, returning an offset in buffer", 2016-03-01)
>>>>    missed that too.
>>>>
>>>>    Unless this tradition has been willfully abandoned, I suggest
>>>> that you
>>>>    add the right reference here, and also (in retrospect) to
>>>>    build_append_named_dword().
>>>>
>>>>
>>>>        +int
>>>>        +build_append_named_qword(GArray *array, const char
>>>> *name_format, ...)
>>>>        +{
>>>>        +    int offset;
>>>>        +    va_list ap;
>>>>        +
>>>>        +    build_append_byte(array, 0x08); /* NameOp */
>>>>        +    va_start(ap, name_format);
>>>>        +    build_append_namestringv(array, name_format, ap);
>>>>        +    va_end(ap);
>>>>        +
>>>>        +    build_append_byte(array, 0x0E); /* QWordPrefix */
>>>>        +
>>>>        +    offset = array->len;
>>>>        +    build_append_int_noprefix(array, 0x00000000, 8);
>>>>
>>>>
>>>>    (4) I guess the constant should be updated here too, for consistency
>>>>    with the comment.
>>>>
>>>>    The rest looks okay. (I didn't verify 0x0E == QWordPrefix
>>>> specifically,
>>>>    because an error there would break the functionality immediately, and
>>>>    you'd notice.)
>>>>
>>>>    Thanks!
>>>>    Laszlo
>>>>
>>>>
>>>>        +    assert(array->len == offset + 8);
>>>>        +
>>>>        +    return offset;
>>>>        +}
>>>>        +
>>>>        static GPtrArray *alloc_list;
>>>>
>>>>        static Aml *aml_alloc(void)
>>>>        diff --git a/include/hw/acpi/aml-build.h
>>>> b/include/hw/acpi/aml-build.h
>>>>        index 559326c..dbf63cf 100644
>>>>        --- a/include/hw/acpi/aml-build.h
>>>>        +++ b/include/hw/acpi/aml-build.h
>>>>        @@ -385,6 +385,10 @@ int
>>>>        build_append_named_dword(GArray *array, const char
>>>> *name_format, ...)
>>>>        GCC_FMT_ATTR(2, 3);
>>>>
>>>>        +int
>>>>        +build_append_named_qword(GArray *array, const char
>>>> *name_format, ...)
>>>>        +GCC_FMT_ATTR(2, 3);
>>>>        +
>>>>        void build_srat_memory(AcpiSratMemoryAffinity *numamem,
>>>> uint64_t base,
>>>>                               uint64_t len, int node,
>>>> MemoryAffinityFlags
>>>>        flags);
>>>>
>>>>
>>>> —Ben
>