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()))?;
 

vmm/src/cpu.rs

@@ -17,6 +17,7 @@ use crate::config::CpusConfig;
 use crate::device_manager::DeviceManager;
 use crate::memory_manager::MemoryManager;
 use crate::seccomp_filters::{get_seccomp_filter, Thread};
+use crate::vm::physical_bits;
 use crate::CPU_MANAGER_SNAPSHOT_ID;
 #[cfg(feature = "acpi")]
 use acpi_tables::{aml, aml::Aml, sdt::SDT};
@@ -259,12 +260,19 @@ impl Vcpu {
         vm_memory: &GuestMemoryAtomic<GuestMemoryMmap>,
         #[cfg(target_arch = "x86_64")] cpuid: CpuId,
         #[cfg(target_arch = "x86_64")] kvm_hyperv: bool,
+        phys_bits: u8,
     ) -> Result<()> {
         #[cfg(target_arch = "aarch64")]
         {
             self.init(vm)?;
-            self.mpidr = arch::configure_vcpu(&self.vcpu, self.id, kernel_entry_point, vm_memory)
-                .map_err(Error::VcpuConfiguration)?;
+            self.mpidr = arch::configure_vcpu(
+                &self.vcpu,
+                self.id,
+                kernel_entry_point,
+                vm_memory,
+                phys_bits,
+            )
+            .map_err(Error::VcpuConfiguration)?;
         }
 
         #[cfg(target_arch = "x86_64")]
@@ -275,6 +283,7 @@ impl Vcpu {
             vm_memory,
             cpuid,
             kvm_hyperv,
+            phys_bits,
         )
         .map_err(Error::VcpuConfiguration)?;
 
@@ -703,6 +712,8 @@ impl CpuManager {
         } else {
             let vm_memory = self.vm_memory.clone();
 
+            let phys_bits = physical_bits(self.config.max_phys_bits);
+
             #[cfg(target_arch = "x86_64")]
             vcpu.lock()
                 .unwrap()
@@ -711,13 +722,14 @@ impl CpuManager {
                     &vm_memory,
                     self.cpuid.clone(),
                     self.config.kvm_hyperv,
+                    phys_bits,
                 )
                 .expect("Failed to configure vCPU");
 
             #[cfg(target_arch = "aarch64")]
             vcpu.lock()
                 .unwrap()
-                .configure(&self.vm, entry_point, &vm_memory)
+                .configure(&self.vm, entry_point, &vm_memory, phys_bits)
                 .expect("Failed to configure vCPU");
         }
 

vmm/src/vm.rs

@@ -433,7 +433,7 @@ impl VmmOps for VmOps {
     }
 }
 
-fn physical_bits(max_phys_bits: Option<u8>) -> u8 {
+pub fn physical_bits(max_phys_bits: Option<u8>) -> u8 {
     let host_phys_bits = get_host_cpu_phys_bits();
     cmp::min(host_phys_bits, max_phys_bits.unwrap_or(host_phys_bits))
 }