Re: [Xen-devel] [PATCH RFC 1/2] linux/vnuma: vnuma support for pv guest

[Matt Wilson <msw@xxxxxxxxxx>]

On Wed, Aug 28, 2013 at 12:01:48PM -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, Aug 27, 2013 at 06:37:35PM -0700, Matt Wilson wrote:
> > On Tue, Aug 27, 2013 at 06:27:15PM -0700, Matt Wilson wrote:
> > > On Tue, Aug 27, 2013 at 04:52:59AM -0400, Elena Ufimtseva wrote:
> > > > Uses subop hypercall to request XEN about vnuma topology.
> > > > Sets the memory blocks (aligned by XEN), cpus, distance table
> > > > on boot. NUMA support should be compiled in kernel.
> > > 
> > > Are we *really sure* that we want to go this route for PV vNUMA?
> > > Couldn't we build just enough(tm) of the ACPI tables to express the
> > > NUMA topology when constructing the domain? That's what we do for the
> > > e820 map.
> > 
> > Ignore me somewhat, since the e820 information is retrieved via
> > hypercall similar to what you're proposing.
> > 
> > Still, if there's some way that we can reuse existing Linux code
> > rather than bolting on a completely parallel mechanism to set this up
> > under PV I think it'd be better.
> 
> That would also parallel the work you do with ACPI right?

Yes.

> We could enable ACPI parsing in a PV guest and provide one table - the
> SLIT (or SRAT).

Right, it'd be the SRAT table for the resource affinity and a SLIT
table for the locality/distance information.

> But I don't know enough about SRAT to know whether this is something
> that represents truly everything we need?

The SRAT table has processor objects and memory objects. A processor
object maps a logical processor number to its initial APIC ID and
provides the node information. A memory object specifies the start and
length for a memory region and provides the node information.

For SLIT, the entries are a matrix of distances.

Here are the structs:

struct acpi_20_srat_processor {
    uint8_t type;
    uint8_t length;
    uint8_t domain;
    uint8_t apic_id;
    uint32_t flags;
    uint8_t sapic_id;
    uint8_t domain_hi[3];
    uint32_t reserved;
};

struct acpi_20_srat_memory {
    uint8_t type;
    uint8_t length;
    uint8_t domain;
    uint8_t domain_hi[3];      /* this is ACPI 3.0, reserved in 2.0 */
    uint16_t reserved;
    uint32_t base_address_lo;
    uint32_t base_address_hi;
    uint32_t length_lo;
    uint32_t length_hi;
    uint32_t reserved2;
    uint32_t flags;
    uint32_t reserved3[2];
};

struct acpi_20_slit {
    struct acpi_header header;
    uint64_t nr_sys_loc;
    uint8_t  entry[];
};

--msw

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