[PATCH] hw/loongarch: Fix ACPI processor id off-by-one error

[Jiajie Chen <c@jia.je>]

In hw/acpi/aml-build.c:build_pptt() function, the code assumes that the
ACPI processor id equals to the cpu index, for example if we have 8
cpus, then the ACPI processor id should be in range 0-7.

However, in hw/loongarch/acpi-build.c:build_madt() function we broke the
assumption. If we have 8 cpus again, the ACPI processor id in MADT table
would be in range 1-8. It violates the following description taken from
ACPI spec 6.4 table 5.138:

If the processor structure represents an actual processor, this field
must match the value of ACPI processor ID field in the processor’s entry
in the MADT.

It will break the latest Linux 6.5-rc6 with the
following error message:

ACPI PPTT: PPTT table found, but unable to locate core 7 (8)
Invalid BIOS PPTT

Here 7 is the last cpu index, 8 is the ACPI processor id learned from
MADT.

With this patch, Linux can properly detect SMT threads when "-smp
8,sockets=1,cores=4,threads=2" is passed:

Thread(s) per core:  2
Core(s) per socket:  2
Socket(s):           2

The detection of number of sockets is still wrong, but that is out of
scope of the commit.

Signed-off-by: Jiajie Chen <c@jia.je>
---
 hw/loongarch/acpi-build.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/loongarch/acpi-build.c b/hw/loongarch/acpi-build.c
index 0b62c3a2f7..ae292fc543 100644
--- a/hw/loongarch/acpi-build.c
+++ b/hw/loongarch/acpi-build.c
@@ -127,7 +127,7 @@ build_madt(GArray *table_data, BIOSLinker *linker, LoongArchMachineState *lams)
         build_append_int_noprefix(table_data, 17, 1);    /* Type */
         build_append_int_noprefix(table_data, 15, 1);    /* Length */
         build_append_int_noprefix(table_data, 1, 1);     /* Version */
-        build_append_int_noprefix(table_data, i + 1, 4); /* ACPI Processor ID */
+        build_append_int_noprefix(table_data, i, 4);     /* ACPI Processor ID */
         build_append_int_noprefix(table_data, arch_id, 4); /* Core ID */
         build_append_int_noprefix(table_data, 1, 4);     /* Flags */
     }
-- 
2.41.0