build: Fixed build errors and warnings on AArch64

This is a preparing commit to build and test CH on AArch64. All building
issues were fixed, but no functionality was introduced.
For X86, the logic of code was not changed at all.
For ARM, the architecture specific part is still empty. And we applied
some tricks to workaround lint warnings. But such code will be replaced
later by other commits with real functionality.

Signed-off-by: Michael Zhao <michael.zhao@arm.com>

arch/src/x86_64/mod.rs

@@ -13,9 +13,9 @@ pub mod layout;
 #[cfg(not(feature = "acpi"))]
 mod mptable;
 pub mod regs;
-
 use crate::InitramfsConfig;
 use crate::RegionType;
+use kvm_ioctls::*;
 use linux_loader::loader::bootparam::{boot_params, setup_header};
 use linux_loader::loader::elf::start_info::{
     hvm_memmap_table_entry, hvm_modlist_entry, hvm_start_info,
@@ -459,6 +459,47 @@ pub fn initramfs_load_addr(
     Ok(aligned_addr)
 }
 
+pub fn get_host_cpu_phys_bits() -> u8 {
+    use std::arch::x86_64;
+    unsafe {
+        let leaf = x86_64::__cpuid(0x8000_0000);
+
+        // Detect and handle AMD SME (Secure Memory Encryption) properly.
+        // Some physical address bits may become reserved when the feature is enabled.
+        // See AMD64 Architecture Programmer's Manual Volume 2, Section 7.10.1
+        let reduced = if leaf.eax >= 0x8000_001f
+            && leaf.ebx == 0x6874_7541    // Vendor ID: AuthenticAMD
+            && leaf.ecx == 0x444d_4163
+            && leaf.edx == 0x6974_6e65
+            && x86_64::__cpuid(0x8000_001f).eax & 0x1 != 0
+        {
+            (x86_64::__cpuid(0x8000_001f).ebx >> 6) & 0x3f
+        } else {
+            0
+        };
+
+        if leaf.eax >= 0x8000_0008 {
+            let leaf = x86_64::__cpuid(0x8000_0008);
+            ((leaf.eax & 0xff) - reduced) as u8
+        } else {
+            36
+        }
+    }
+}
+
+pub fn check_required_kvm_extensions(kvm: &Kvm) -> super::Result<()> {
+    if !kvm.check_extension(Cap::SignalMsi) {
+        return Err(super::Error::CapabilityMissing(Cap::SignalMsi));
+    }
+    if !kvm.check_extension(Cap::TscDeadlineTimer) {
+        return Err(super::Error::CapabilityMissing(Cap::TscDeadlineTimer));
+    }
+    if !kvm.check_extension(Cap::SplitIrqchip) {
+        return Err(super::Error::CapabilityMissing(Cap::SplitIrqchip));
+    }
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;