vmm: cpu: Set CPU physical bits based on user input

If the user specified a maximum physical bits value through the
`max_phys_bits` option from `--cpus` parameter, the guest CPUID
will be patched accordingly to ensure the guest will find the
right amount of physical bits.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

arch/src/aarch64/mod.rs

@@ -63,6 +63,7 @@ pub fn configure_vcpu(
     id: u8,
     kernel_entry_point: Option<EntryPoint>,
     vm_memory: &GuestMemoryAtomic<GuestMemoryMmap>,
+    _phys_bits: u8,
 ) -> super::Result<u64> {
     if let Some(kernel_entry_point) = kernel_entry_point {
         regs::setup_regs(

arch/src/x86_64/mod.rs

@@ -337,6 +337,7 @@ pub fn configure_vcpu(
     vm_memory: &GuestMemoryAtomic<GuestMemoryMmap>,
     cpuid: CpuId,
     kvm_hyperv: bool,
+    phys_bits: u8,
 ) -> super::Result<()> {
     let mut cpuid = cpuid;
     CpuidPatch::set_cpuid_reg(&mut cpuid, 0xb, None, CpuidReg::EDX, u32::from(id));
@@ -410,6 +411,13 @@ pub fn configure_vcpu(
             .map_err(|_| Error::PopulatingCpuid)?;
     }
 
+    // Set CPU physical bits
+    for entry in cpuid.as_mut_slice().iter_mut() {
+        if entry.function == 0x8000_0008 {
+            entry.eax = (entry.eax & 0xffff_ff00) | (phys_bits as u32 & 0xff);
+        }
+    }
+
     fd.set_cpuid2(&cpuid)
         .map_err(|e| Error::SetSupportedCpusFailed(e.into()))?;