Hi,
On 10/14/21 3:22 PM, Yanan Wang wrote:
> From: Andrew Jones <drjo...@redhat.com>
>
> Add the Processor Properties Topology Table (PPTT) used to
> describe CPU topology information to ACPI guests.
>
> Note, a DT-boot Linux guest with a non-flat CPU topology will
> see socket and core IDs being sequential integers starting
> from zero, which is different from ACPI-boot Linux guest,
> e.g. with -smp 4,sockets=2,cores=2,threads=1
>
> a DT boot produces:
>
> cpu: 0 package_id: 0 core_id: 0
> cpu: 1 package_id: 0 core_id: 1
> cpu: 2 package_id: 1 core_id: 0
> cpu: 3 package_id: 1 core_id: 1
>
> an ACPI boot produces:
>
> cpu: 0 package_id: 36 core_id: 0
> cpu: 1 package_id: 36 core_id: 1
> cpu: 2 package_id: 96 core_id: 2
> cpu: 3 package_id: 96 core_id: 3
>
> This is due to several reasons:
>
> 1) DT cpu nodes do not have an equivalent field to what the PPTT
> ACPI Processor ID must be, i.e. something equal to the MADT CPU
> UID or equal to the UID of an ACPI processor container. In both
> ACPI cases those are platform dependant IDs assigned by the
> vendor.
>
> 2) While QEMU is the vendor for a guest, if the topology specifies
> SMT (> 1 thread), then, with ACPI, it is impossible to assign a
> core-id the same value as a package-id, thus it is not possible
> to have package-id=0 and core-id=0. This is because package and
> core containers must be in the same ACPI namespace and therefore
> must have unique UIDs.
>
> 3) ACPI processor containers are not mandatorily required for PPTT
> tables to be used and, due to the limitations of which IDs are
> selected described above in (2), they are not helpful for QEMU,
> so we don't build them with this patch. In the absence of them,
> Linux assigns its own unique IDs. The maintainers have chosen not
> to use counters from zero, but rather ACPI table offsets, which
> explains why the numbers are so much larger than with DT.
>
> 4) When there is no SMT (threads=1) the core IDs for ACPI boot guests
> match the logical CPU IDs, because these IDs must be equal to the
> MADT CPU UID (as no processor containers are present), and QEMU
> uses the logical CPU ID for these MADT IDs.
>
> So in summary, with QEMU as the vendor for the guests, we simply
> use sequential integers starting from zero for the non-leaf nodes
> but with ID-valid flag unset, so that guest will ignore them and
> use table offsets as unique container IDs. And we use logical CPU
> IDs for the leaf nodes with the ID-valid flag set, which will be
> consistent with MADT.
>
> Signed-off-by: Andrew Jones <drjo...@redhat.com>
> Co-developed-by: Yanan Wang <wangyana...@huawei.com>
> Signed-off-by: Yanan Wang <wangyana...@huawei.com>
> Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> hw/acpi/aml-build.c | 60 +++++++++++++++++++++++++++++++++++++
> include/hw/acpi/aml-build.h | 3 ++
> 2 files changed, 63 insertions(+)
>
> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> index b7b9db6888..0d50e88e9d 100644
> --- a/hw/acpi/aml-build.c
> +++ b/hw/acpi/aml-build.c
> @@ -1990,6 +1990,66 @@ void build_processor_hierarchy_node(GArray *tbl,
> uint32_t flags,
> }
> }
>
> +/* ACPI 6.2: 5.2.29 Processor Properties Topology Table (PPTT) */
> +void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
> + const char *oem_id, const char *oem_table_id)
> +{
> + int pptt_start = table_data->len;
> + int uid = 0;
> + int socket;
> + AcpiTable table = { .sig = "PPTT", .rev = 2,
> + .oem_id = oem_id, .oem_table_id = oem_table_id };
Table 5-149 of 6.2 spec (6.2 May 2017) tells the rev shall be 1. Or is
it an erratum somewhere I did miss?
I would also add the spec version in the commit msg.
> +
> + acpi_table_begin(&table, table_data);
> +
> + for (socket = 0; socket < ms->smp.sockets; socket++) {
> + uint32_t socket_offset = table_data->len - pptt_start;
> + int core;
> +
> + build_processor_hierarchy_node(
> + table_data,
> + /*
> + * ACPI 6.2 - Physical package
> + * represents the boundary of a physical package
> + */
> + (1 << 0),
> + 0, socket, NULL, 0);
I see we set an ACPI process ID but in the meantime the ACPI processor
ID valid flag is not set. I am not sure I fully catch the meaning of
this latter but just to double check if this is done on purpose. Maybe
wort a general comment as this also happens below.
> +
> + for (core = 0; core < ms->smp.cores; core++) {
> + uint32_t core_offset = table_data->len - pptt_start;
> + int thread;
> +
> + if (ms->smp.threads > 1) {
> + build_processor_hierarchy_node(
> + table_data,
> + /*
> + * ACPI 6.2 - Physical package
> + * doesn't represent the boundary of a physical package
> + */
> + (0 << 0),
would rather say (0 << 0) /* not a physical package */ and same elsewhere
> + socket_offset, core, NULL, 0);
> +
> + for (thread = 0; thread < ms->smp.threads; thread++) {
> + build_processor_hierarchy_node(
> + table_data,
> + (1 << 1) | /* ACPI 6.2 - ACPI Processor ID valid */
> + (1 << 2) | /* ACPI 6.3 - Processor is a Thread */
So the references look globaly confusing to me. Either it complies to
6.2 or to 6.3. Looks ir rather complies with 6.3. To me, this needs to
be clarified. I would also add the reference it complies to in the
commit msg.
> + (1 << 3), /* ACPI 6.3 - Node is a Leaf */
> + core_offset, uid++, NULL, 0);
> + }
> + } else {
> + build_processor_hierarchy_node(
> + table_data,
> + (1 << 1) | /* ACPI 6.2 - ACPI Processor ID valid */
> + (1 << 3), /* ACPI 6.3 - Node is a Leaf */
> + socket_offset, uid++, NULL, 0);
> + }
> + }
> + }
> +
> + acpi_table_end(linker, &table);
> +}
> +
> /* build rev1/rev3/rev5.1 FADT */
> void build_fadt(GArray *tbl, BIOSLinker *linker, const AcpiFadtData *f,
> const char *oem_id, const char *oem_table_id)
> diff --git a/include/hw/acpi/aml-build.h b/include/hw/acpi/aml-build.h
> index 2c457c8f17..b92706388c 100644
> --- a/include/hw/acpi/aml-build.h
> +++ b/include/hw/acpi/aml-build.h
> @@ -493,6 +493,9 @@ void build_processor_hierarchy_node(GArray *tbl, uint32_t
> flags,
> uint32_t parent, uint32_t id,
> uint32_t *priv_rsrc, uint32_t priv_num);
>
> +void build_pptt(GArray *table_data, BIOSLinker *linker, MachineState *ms,
> + const char *oem_id, const char *oem_table_id);
> +
> void build_fadt(GArray *tbl, BIOSLinker *linker, const AcpiFadtData *f,
> const char *oem_id, const char *oem_table_id);
>
>
Thanks
Eric
