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

[Ben Warren]

> On Jan 25, 2017, at 4:48 PM, Laszlo Ersek <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> 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 wrote:
>>> 
>>>        From: Ben Warren <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>
>>>        ---
>>>        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 
> <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 
> <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.  

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:

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

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