On Wed, 20 Apr 2022 13:19:34 +0800
Gavin Shan <gs...@redhat.com> wrote:
> Hi Igor,
>
> On 4/19/22 4:54 PM, Igor Mammedov wrote:
> > On Thu, 14 Apr 2022 08:33:29 +0800
> > Gavin Shan <gs...@redhat.com> wrote:
> >> On 4/13/22 9:52 PM, Igor Mammedov wrote:
> >>> On Sun, 3 Apr 2022 22:59:53 +0800
> >>> Gavin Shan <gs...@redhat.com> wrote:
> >>>
> >>>> When the PPTT table is built, the CPU topology is re-calculated, but
> >>>> it's unecessary because the CPU topology has been populated in
> >>>> virt_possible_cpu_arch_ids() on arm/virt machine.
> >>>>
> >>>> This reworks build_pptt() to avoid by reusing the existing one in
> >>>> ms->possible_cpus. Currently, the only user of build_pptt() is
> >>>> arm/virt machine.
> >>>>
> >>>> Signed-off-by: Gavin Shan <gs...@redhat.com>
> >>>> ---
> >>>> hw/acpi/aml-build.c | 100 +++++++++++++++++---------------------------
> >>>> 1 file changed, 38 insertions(+), 62 deletions(-)
> >>>>
> >>>> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> >>>> index 4086879ebf..4b0f9df3e3 100644
> >>>> --- a/hw/acpi/aml-build.c
> >>>> +++ b/hw/acpi/aml-build.c
> >>>> @@ -2002,86 +2002,62 @@ void build_pptt(GArray *table_data, BIOSLinker
> >>>> *linker, MachineState *ms,
> >>>> const char *oem_id, const char *oem_table_id)
> >>>> {
> >>>> MachineClass *mc = MACHINE_GET_CLASS(ms);
> >>>> - GQueue *list = g_queue_new();
> >>>> - guint pptt_start = table_data->len;
> >>>> - guint parent_offset;
> >>>> - guint length, i;
> >>>> - int uid = 0;
> >>>> - int socket;
> >>>> + CPUArchIdList *cpus = ms->possible_cpus;
> >>>> + int64_t socket_id = -1, cluster_id = -1, core_id = -1;
> >>>> + uint32_t socket_offset, cluster_offset, core_offset;
> >>>> + uint32_t pptt_start = table_data->len;
> >>>> + int n;
> >>>> AcpiTable table = { .sig = "PPTT", .rev = 2,
> >>>> .oem_id = oem_id, .oem_table_id =
> >>>> oem_table_id };
> >>>>
> >>>> acpi_table_begin(&table, table_data);
> >>>>
> >>>> - for (socket = 0; socket < ms->smp.sockets; socket++) {
> >>>> - g_queue_push_tail(list,
> >>>> - GUINT_TO_POINTER(table_data->len - pptt_start));
> >>>> - build_processor_hierarchy_node(
> >>>> - table_data,
> >>>> - /*
> >>>> - * Physical package - represents the boundary
> >>>> - * of a physical package
> >>>> - */
> >>>> - (1 << 0),
> >>>> - 0, socket, NULL, 0);
> >>>> - }
> >>>> + for (n = 0; n < cpus->len; n++) {
> >>>
> >>>> + if (cpus->cpus[n].props.socket_id != socket_id) {
> >>>> + socket_id = cpus->cpus[n].props.socket_id;
> >>>
> >>> this relies on cpus->cpus[n].props.*_id being sorted form top to down
> >>> levels
> >>> I'd add here and for other container_id an assert() that checks for that
> >>> specific ID goes in only one direction, to be able to detect when rule is
> >>> broken.
> >>>
> >>> otherwise on may end up with duplicate containers silently.
> >>>
> >>
> >> Exactly. cpus->cpus[n].props.*_id is sorted as you said in
> >> virt_possible_cpu_arch_ids().
> >> The only user of build_pptt() is arm/virt machine. So it's fine. However,
> >> I think I
> >> may need add comments for this in v6.
> >>
> >> /*
> >> * This works with the assumption that cpus[n].props.*_id has been
> >> * sorted from top to down levels in mc->possible_cpu_arch_ids().
> >> * Otherwise, the unexpected and duplicate containers will be
> >> created.
> >> */
> >>
> >> The implementation in v3 looks complicated, but comprehensive. The one
> >> in this revision (v6) looks simple, but the we're losing flexibility :)
> >
> >
> > comment is not enough, as it will break silently that's why I suggested
> > sprinkling asserts() here.
> >
>
> I don't think it breaks anything. Duplicated PPTT entries are allowed in
> linux at least. The IDs in the duplicated PPTT entries should be same.
> Otherwise, the exposed CPU topology is really broken.
Spec doesn't say anything about allowing duplicate entries so I'd rather
avoid that (if you find a such provision in spec then put a reference
in this commit message to end discussion on duplicates).
>
> I don't think it's harmful to add the check and assert, so I will introduce
> a helper function like below in v7. Sadly that v6 was posted before I received
> your confirm. Igor, could you please the changes, to be included into v7,
> looks good to you? The complete patch is also attached :)
>
> +static bool pptt_entry_exists(MachineState *ms, int n, bool check_socket_id,
> + bool check_cluster_id, bool check_core_id)
> +{
> + CPUArchId *cpus = ms->possible_cpus->cpus;
> + CpuInstanceProperties *t = &cpus[n].props;
> + CpuInstanceProperties *s;
> + bool match;
> + int i;
> +
> + for (i = 0; i < n; i++) {
Wouldn't it make whole thing O(n^2) in worst case?
I suggest put asserts directly into build_pptt() and considering that
it relies on ids being sorted, do something like this:
assert(foo_id_val > previous_id)
which will ensure that id doesn't jump back unexpectedly
> + match = true;
> + s = &cpus[i].props;
> +
> + if (check_socket_id && s->socket_id != t->socket_id) {
> + match = false;
> + }
> +
> + if (match && check_cluster_id && s->cluster_id != t->cluster_id) {
> + match = false;
> + }
> +
> + if (match && check_core_id && s->core_id != t->core_id) {
> + match = false;
> + }
> +
> + if (match) {
> + return true;
> + }
> + }
> +
> + return false;
> +}
>
> The following assert() will be applied in build_pptt():
>
> assert(!pptt_entry_exists(ms, n, true, false, false)); /* socket */
> assert(!pptt_entry_exists(ms, n, true, true, false)); /* cluster */
> assert(!pptt_entry_exists(ms, n, true,
> mc->smp_props.clusters_supported, true)); /* core
> */
>
> Thanks,
> Gavin
>
