pvh/arch: Introduce EntryPoint struct

In order to properly configure the initial vCPU register state
and boot parameters in guest memory, we must specify which
boot protocol to use with the kernel entry point address.

Create an EntryPoint struct that contains the required
information. This structure will later be used in the vCPU
configuration methods to set the appropriate initial
conditions for the guest.

Signed-off-by: Colin Percival <cperciva@freebsd.org>
Co-authored-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>

Author: cperciva

src/arch/src/lib.rs

@@ -65,3 +65,32 @@ impl fmt::Display for DeviceType {
         write!(f, "{:?}", self)
     }
 }
+
+/// Suported boot protocols for
+#[derive(Debug, Copy, Clone)]
+pub enum BootProtocol {
+    /// Linux 64-bit boot protocol
+    LinuxBoot,
+    /// PVH boot protocol (x86/HVM direct boot ABI)
+    PvhBoot,
+}
+
+impl fmt::Display for BootProtocol {
+    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        match self {
+            BootProtocol::LinuxBoot => write!(f, "Linux 64-bit boot protocol"),
+            BootProtocol::PvhBoot => write!(f, "PVH boot protocol"),
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone)]
+/// Specifies the entry point address where the guest must start
+/// executing code, as well as which boot protocol is to be used
+/// to configure the guest initial state.
+pub struct EntryPoint {
+    /// Address in guest memory where the guest must start execution
+    pub entry_addr: vm_memory::GuestAddress,
+    /// Specifies which boot protocol to use
+    pub protocol: BootProtocol,
+}

src/vmm/src/builder.rs

@@ -9,7 +9,7 @@ use std::io::{self, Read, Seek, SeekFrom};
 use std::os::unix::io::{AsRawFd, RawFd};
 use std::sync::{Arc, Mutex};
 
-use arch::InitrdConfig;
+use arch::{BootProtocol, EntryPoint, InitrdConfig};
 #[cfg(target_arch = "x86_64")]
 use cpuid::common::is_same_model;
 use devices::legacy::serial::ReadableFd;
@@ -22,6 +22,7 @@ use libc::EFD_NONBLOCK;
 use linux_loader::cmdline::Cmdline as LoaderKernelCmdline;
 #[cfg(target_arch = "x86_64")]
 use linux_loader::loader::elf::Elf as Loader;
+use linux_loader::loader::elf::PvhBootCapability;
 #[cfg(target_arch = "aarch64")]
 use linux_loader::loader::pe::PE as Loader;
 use linux_loader::loader::KernelLoader;
@@ -334,7 +335,7 @@ pub fn build_microvm_for_boot(
     let guest_memory =
         create_guest_memory(vm_resources.vm_config().mem_size_mib, track_dirty_pages)?;
     let vcpu_config = vm_resources.vcpu_config();
-    let entry_addr = load_kernel(boot_config, &guest_memory)?;
+    let entry_point = load_kernel(boot_config, &guest_memory)?;
     let initrd = load_initrd_from_config(boot_config, &guest_memory)?;
     // Clone the command-line so that a failed boot doesn't pollute the original.
     #[allow(unused_mut)]
@@ -407,7 +408,7 @@ pub fn build_microvm_for_boot(
         &vmm,
         vcpus.as_mut(),
         vcpu_config,
-        entry_addr,
+        entry_point.entry_addr,
         &initrd,
         boot_cmdline,
     )?;
@@ -633,7 +634,7 @@ pub fn create_guest_memory(
 fn load_kernel(
     boot_config: &BootConfig,
     guest_memory: &GuestMemoryMmap,
-) -> std::result::Result<GuestAddress, StartMicrovmError> {
+) -> std::result::Result<EntryPoint, StartMicrovmError> {
     let mut kernel_file = boot_config
         .kernel_file
         .try_clone()
@@ -657,7 +658,21 @@ fn load_kernel(
     )
     .map_err(StartMicrovmError::KernelLoader)?;
 
-    Ok(entry_addr.kernel_load)
+    let mut entry_point_addr: GuestAddress = entry_addr.kernel_load;
+    let mut boot_prot: BootProtocol = BootProtocol::LinuxBoot;
+
+    if cfg!(target_arch = "x86_64") {
+        if let PvhBootCapability::PvhEntryPresent(pvh_entry_addr) = entry_addr.pvh_boot_cap {
+            // Use the PVH kernel entry point to boot the guest
+            entry_point_addr = pvh_entry_addr;
+            boot_prot = BootProtocol::PvhBoot;
+        }
+    }
+
+    Ok(EntryPoint {
+        entry_addr: entry_point_addr,
+        protocol: boot_prot,
+    })
 }
 
 fn load_initrd_from_config(