pvh/arch-x86_64: Initialize vCPU regs for PVH

Set the initial values of the KVM vCPU registers as specified in
the PVH boot ABI:

https://xenbits.xen.org/docs/unstable/misc/pvh.html

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

Author: cperciva

0001-pvh-arch-Introduce-EntryPoint-struct.patch

@@ -0,0 +1,132 @@
+From e0b0f71e3f3b6fcd53c49875b18d0d5dbdd53e88 Mon Sep 17 00:00:00 2001
+From: Colin Percival <cperciva@freebsd.org>
+Date: Sun, 2 Oct 2022 10:42:24 -0700
+Subject: [PATCH 1/3] 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>
+---
+ src/arch/src/lib.rs    | 29 +++++++++++++++++++++++++++++
+ src/vmm/src/builder.rs | 25 ++++++++++++++++++++-----
+ 2 files changed, 49 insertions(+), 5 deletions(-)
+
+diff --git a/src/arch/src/lib.rs b/src/arch/src/lib.rs
+index 7d025f39..950676cf 100644
+--- a/src/arch/src/lib.rs
++++ b/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,
++}
+diff --git a/src/vmm/src/builder.rs b/src/vmm/src/builder.rs
+index 09506087..5c2828bc 100644
+--- a/src/vmm/src/builder.rs
++++ b/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,
+     )?;
+@@ -636,7 +637,7 @@ 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()
+@@ -660,7 +661,21 @@ 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(
+-- 
+2.38.1
+