Re: [Qemu-devel] [PATCH for-2.1 2/2] i386/acpi-build: support hotplug of VCPU with APIC ID 0xFF

[Laszlo Ersek <lersek@redhat.com>]

On 03/16/14 13:31, Michael S. Tsirkin wrote:
> On Fri, Mar 14, 2014 at 11:22:52PM +0100, Laszlo Ersek wrote:
>> Building on the previous patch, raise the maximal count of processor
>> objects / NTFY branches / CPON elements from 255 to 256. This allows the
>> VCPU with APIC ID 0xFF to be hotplugged.
>>
>> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
>> ---
>>  hw/i386/acpi-build.c | 16 +++++++++++-----
>>  1 file changed, 11 insertions(+), 5 deletions(-)
>>
>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>> index 2bbefb5..51162fc 100644
>> --- a/hw/i386/acpi-build.c
>> +++ b/hw/i386/acpi-build.c
>> @@ -999,11 +999,15 @@ build_ssdt(GArray *table_data, GArray *linker,
>>             AcpiCpuInfo *cpu, AcpiPmInfo *pm, AcpiMiscInfo *misc,
>>             PcPciInfo *pci, PcGuestInfo *guest_info)
>>  {
>> -    int acpi_cpus = MIN(0xff, guest_info->apic_id_limit);
> 
> Maybe just make this line
>      int acpi_cpus = guest_info->apic_id_limit;
> and then the patch will be smaller.

I did think of that, but I didn't like the unchecked unsigned --> int
conversion. The limit checks below cover that too.

Also, the patch renders the function similar to the other acpi builder
functions; there are a handful of loops that directly name
"guest_info->apic_id_limit" in their controlling expressions.

Anyway, would you be OK with a patch that did the assignment you suggest
(rather than modifying the loops), and kept the BUILD_BUG and the
g_assert below?

Thanks
Laszlo

> 
>>      int ssdt_start = table_data->len;
>>      uint8_t *ssdt_ptr;
>>      int i;
>>  
>> +    /* The current AML generator can cover the APIC ID range [0..255],
>> +     * inclusive, for VCPU hotplug. */
>> +    QEMU_BUILD_BUG_ON(ACPI_CPU_HOTPLUG_ID_LIMIT > 256);
>> +    g_assert(guest_info->apic_id_limit <= ACPI_CPU_HOTPLUG_ID_LIMIT);
>> +
>>      /* Copy header and patch values in the S3_ / S4_ / S5_ packages */
>>      ssdt_ptr = acpi_data_push(table_data, sizeof(ssdp_misc_aml));
>>      memcpy(ssdt_ptr, ssdp_misc_aml, sizeof(ssdp_misc_aml));
>> @@ -1029,7 +1033,7 @@ build_ssdt(GArray *table_data, GArray *linker,
>>          build_append_nameseg(sb_scope, "_SB_");
>>  
>>          /* build Processor object for each processor */
>> -        for (i = 0; i < acpi_cpus; i++) {
>> +        for (i = 0; i < guest_info->apic_id_limit; i++) {
>>              uint8_t *proc = acpi_data_push(sb_scope, ACPI_PROC_SIZEOF);
>>              memcpy(proc, ACPI_PROC_AML, ACPI_PROC_SIZEOF);
>>              proc[ACPI_PROC_OFFSET_CPUHEX] = acpi_get_hex(i >> 4);
>> @@ -1042,7 +1046,8 @@ build_ssdt(GArray *table_data, GArray *linker,
>>           *   Method(NTFY, 2) {If (LEqual(Arg0, 0x00)) {Notify(CP00, Arg1)} ...}
>>           */
>>          /* Arg0 = Processor ID = APIC ID */
>> -        build_append_notify_method(sb_scope, "NTFY", "CP%0.02X", acpi_cpus);
>> +        build_append_notify_method(sb_scope, "NTFY", "CP%0.02X",
>> +                                   guest_info->apic_id_limit);
>>  
>>          /* build "Name(CPON, Package() { One, One, ..., Zero, Zero, ... })" */
>>          build_append_byte(sb_scope, 0x08); /* NameOp */
>> @@ -1052,8 +1057,9 @@ build_ssdt(GArray *table_data, GArray *linker,
>>              GArray *package = build_alloc_array();
>>              uint8_t op = 0x13; /* VarPackageOp */
>>  
>> -            build_append_int(package, acpi_cpus); /* VarNumElements */
>> -            for (i = 0; i < acpi_cpus; i++) {
>> +            build_append_int(package,
>> +                             guest_info->apic_id_limit); /* VarNumElements */
>> +            for (i = 0; i < guest_info->apic_id_limit; i++) {
>>                  uint8_t b = test_bit(i, cpu->found_cpus) ? 0x01 : 0x00;
>>                  build_append_byte(package, b);
>>              }
>> -- 
>> 1.8.3.1