Re: [Xen-devel] [PATCH RFC 18/20] libxc/acpi: Build ACPI tables for HVMlite guests

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 06/07/2016 02:17 AM, Jan Beulich wrote:
>>>> On 06.06.16 at 18:59, <boris.ostrovsky@xxxxxxxxxx> wrote:
>> On 06/06/2016 09:29 AM, Jan Beulich wrote:
>>>>>> On 06.04.16 at 03:25, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>>> +#define RESERVED_MEMORY_DYNAMIC_START 0xFC001000
>>>> +#define ACPI_PHYSICAL_ADDRESS         0x000EA020
>>>> +
>>>> +/* Initial allocation for ACPI tables */
>>>> +#define NUM_ACPI_PAGES  16
>>> With which other definitions do these three need to remain in sync?
>> NUM_ACPI_PAGES is private to this file.
>>
>> ACPI_PHYSICAL_ADDRESS (RSDP pointer) needs to be between 0xe0000 and 
>> 0xfffff, I picked this number because that's where most systems that I have 
>> appear to have it. (And by "most" I mean the two that I checked ;-))
> With there not being a BIOS, I can see this being pretty arbitrary.
> Yet in that case I'm not convinced of this getting put at a random
> address in the middle. 

I can put it in the beginning, at 0xe0000.

> Plus I'm not sure I see the connection to the
> reservations done in the E820 map the guest gets to see.

I thought ACPI data is supposed to live in reserved areas (ACPI data,
actually)?

>
>> RESERVED_MEMORY_DYNAMIC_START is one page after DSDT's SystemMemory (aka 
>> ACPI_INFO_PHYSICAL_ADDRESS). But then it looks like PVHv2 doesn't need 
>> SystemMemory so it can be anywhere (and e820 should presumably be aware of 
>> this, which it is not right now)
> So you say there's no connection to the end of hvmloader's window
> for PCI MMIO assignments (an equivalent of which is going to be
> needed for PVHv2)?

I haven't thought about this but then we don't have MMIO hole now. I can
try finding available memory chunk in guest's memory under 4G.

>
>>>> +static int init_acpi_config(struct xc_dom_image *dom,
>>>> +                            struct acpi_config *config)
>>>> +{
>>>> +    xc_interface *xch = dom->xch;
>>>> +    uint32_t domid = dom->guest_domid;
>>>> +    xc_dominfo_t info;
>>>> +    int i, rc;
>>>> +
>>>> +    memset(config, 0, sizeof(*config));
>>>> +
>>>> +    config->dsdt_anycpu = config->dsdt_15cpu = dsdt_empty;
>>>> +    config->dsdt_anycpu_len = config->dsdt_15cpu_len = dsdt_empty_len;
>>> What good does an empty DSDT do? (Perhaps this question is a
>>> result of there not being any description of this change.)
>> DSDT is required to be present by the spec. And ACPICA gets upset if it
>> doesn't see it.
> But my point (also mentioned further down in the original reply) was
> that there's no need for anything if acpi=0. 

Right, but the whole routine will not be called if that's the case (in v1).

> But note that as soon as
> you report processors in MADT, the combined set of tables holding
> AML code can't be empty anymore: Processors need to be
> declared using Processor() (legacy) or Device(). Maybe we don't
> need as much as an ordinary HVM guest, but nothing seems too little.

I will add Processor.

>
>>>> --- a/xen/common/libacpi/build.c
>>>> +++ b/xen/common/libacpi/build.c
>>>> @@ -480,7 +480,7 @@ static int new_vm_gid(struct acpi_config *config)
>>>>      return 1;
>>>>  }
>>>>  
>>>> -void acpi_build_tables(struct acpi_config *config, unsigned int physical)
>>>> +void acpi_build_tables(struct acpi_config *config, unsigned long physical)
>>> I'm having some difficulty seeing how this change belongs here.
>> acpi_build_tables() is called with virtual (i.e. 64-bit) address from libxc.
> Oh - so the parameter name is then wrong?


Yes, it should have a more appropriate name. Like rsdp or something like
that.

-boris


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