[xen master] tools/hvmloader: Retrieve APIC IDs from the APs themselves

[patchbot@xxxxxxx]

commit 9ad0db58c7e2a6bd2b1c0d66ba3b2d73c8d11165
Author:     Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
AuthorDate: Mon Mar 10 09:52:30 2025 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Mar 10 09:52:30 2025 +0100

    tools/hvmloader: Retrieve APIC IDs from the APs themselves
    
    Make it so the APs expose their own APIC IDs in a lookup table (LUT). We
    can use that LUT to populate the MADT, decoupling the algorithm that
    relates CPU IDs and APIC IDs from hvmloader.
    
    Modified the printf to also print the APIC ID of each CPU, as well as
    fixing a (benign) wrong specifier being used for the vcpu id.
    
    Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 tools/firmware/hvmloader/config.h |  2 ++
 tools/firmware/hvmloader/smp.c    | 43 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/tools/firmware/hvmloader/config.h 
b/tools/firmware/hvmloader/config.h
index cd716bf392..b32bcbf4a1 100644
--- a/tools/firmware/hvmloader/config.h
+++ b/tools/firmware/hvmloader/config.h
@@ -48,6 +48,8 @@ extern uint8_t ioapic_version;
 
 #define IOAPIC_ID           0x01
 
+extern uint32_t *cpu_to_apicid;
+
 #define LAPIC_BASE_ADDRESS  0xfee00000
 #define LAPIC_ID(vcpu_id)   ((vcpu_id) * 2)
 
diff --git a/tools/firmware/hvmloader/smp.c b/tools/firmware/hvmloader/smp.c
index 1b940cefd0..341fd6e0b6 100644
--- a/tools/firmware/hvmloader/smp.c
+++ b/tools/firmware/hvmloader/smp.c
@@ -31,9 +31,38 @@
 
 static int ap_callin;
 
+/** True if x2apic support is exposed to the guest. */
+static bool has_x2apic;
+
+/**
+ * Lookup table of APIC IDs.
+ *
+ * Each entry is populated for its respective CPU as they come online. This is
+ * required for generating the MADT with minimal assumptions about ID
+ * relationships.
+ */
+uint32_t *cpu_to_apicid;
+
+static uint32_t read_apic_id(void)
+{
+    uint32_t apic_id;
+
+    if ( has_x2apic )
+        cpuid(0xb, NULL, NULL, NULL, &apic_id);
+    else
+    {
+        cpuid(1, NULL, &apic_id, NULL, NULL);
+        apic_id >>= 24;
+    }
+
+    return apic_id;
+}
+
 static void cpu_setup(unsigned int cpu)
 {
-    printf(" - CPU%d ... ", cpu);
+    uint32_t apicid = cpu_to_apicid[cpu] = read_apic_id();
+
+    printf(" - CPU%u APIC ID %u ... ", cpu, apicid);
     cacheattr_init();
     printf("done.\n");
 
@@ -104,8 +133,20 @@ static void boot_cpu(unsigned int cpu)
 void smp_initialise(void)
 {
     unsigned int i, nr_cpus = hvm_info->nr_vcpus;
+    uint32_t ecx, max_leaf;
+
+    cpuid(0, &max_leaf, NULL, NULL, NULL);
+    if ( max_leaf >= 0xb )
+    {
+        cpuid(1, NULL, NULL, &ecx, NULL);
+        has_x2apic = (ecx >> 21) & 1;
+        if ( has_x2apic )
+            printf("x2APIC supported\n");
+    }
 
     printf("Multiprocessor initialisation:\n");
+    cpu_to_apicid = scratch_alloc(sizeof(*cpu_to_apicid) * nr_cpus,
+                                  sizeof(*cpu_to_apicid));
     cpu_setup(0);
     for ( i = 1; i < nr_cpus; i++ )
         boot_cpu(i);
--
generated by git-patchbot for /home/xen/git/xen.git#master