kernel: remove hand-rolled CPU feature detection module

Delete kernel/src/cpu/features.rs now that all call sites use
cpufeature-based helpers. Drop the features module from cpu/mod.rs and
remove the legacy SvsmPlatform::cpuid(eax, ecx) trait method and the
redundant SnpPlatform override, since CPUID queries are routed through
CpuidBackend and the platform-layer cpuid() wrappers added earlier in
this series.

This completes the migration from locally maintained CPUID tables to the
shared cpufeature crate as the single source of truth for processor
feature definitions.

Signed-off-by: tanish111 <tanishdesai37@gmail.com>

Author: tanish111

kernel/src/cpu/features.rs

@@ -10,7 +10,6 @@ pub mod cpuid;
 pub mod cpuset;
 pub mod efer;
 pub mod extable;
-pub mod features;
 pub mod gdt;
 pub mod idt;
 pub mod ipi;

kernel/src/cpu/mod.rs

@@ -5,7 +5,7 @@
 // Author: Vasant Karasulli <vkarasulli@suse.de>
 
 use crate::cpu::control_regs::{cr0_sse_enable, cr4_osfxsr_enable, cr4_xsave_enable};
-use crate::platform::{cpuid_feature, has_cpuid_feature};
+use crate::platform::{cpuid, has_cpuid_feature};
 use core::arch::asm;
 use core::arch::x86_64::{_xgetbv, _xsetbv};
 use core::sync::atomic::{AtomicU64, Ordering};
@@ -81,7 +81,7 @@ pub fn xsave_area_size() -> u32 {
             subleaf: bit,
             ..XSAVE_SZ
         };
-        let Some(result) = cpuid_feature(&feature) else {
+        let Some(result) = cpuid(&feature) else {
             log::warn!("FP feature {bit:#x} enabled but not present in CPUID");
             continue;
         };

kernel/src/cpu/sse.rs

@@ -214,7 +214,7 @@ mod tests {
     use super::*;
     use crate::cpu::msr::{RdtscpOut, rdtsc, rdtscp, read_msr, write_msr};
     use crate::locking::SpinLock;
-    use crate::platform::cpuid_feature;
+    use crate::platform::cpuid;
     use crate::platform::cpuid_value_or;
     use crate::sev::ghcb::GHCB;
     use crate::sev::utils::raw_vmmcall;
@@ -237,7 +237,7 @@ mod tests {
     #[cfg_attr(not(test_in_svsm), ignore = "Can only be run inside guest")]
     fn test_has_amd_cpuid() {
         if is_test_platform_type(SvsmPlatformType::Snp) {
-            let (ebx, edx, ecx) = cpuid_feature(&MAX_STD_LEAF)
+            let (ebx, edx, ecx) = cpuid(&MAX_STD_LEAF)
                 .map(|r| (r.ebx, r.edx, r.ecx))
                 .unwrap_or((0, 0, 0));
             let vendor_name_bytes = [ebx, edx, ecx].map(|v| v.to_le_bytes()).concat();

kernel/src/cpu/vc.rs

@@ -19,7 +19,7 @@ use snp::SnpPlatform;
 use tdp::TdpPlatform;
 
 use core::arch::asm;
-use core::arch::x86_64::{__cpuid_count, CpuidResult};
+use core::arch::x86_64::CpuidResult;
 
 use core::fmt::Debug;
 use core::mem::MaybeUninit;
@@ -184,15 +184,6 @@ pub trait SvsmPlatform: Sync {
         hypercall_pages: &hyperv::HypercallPagesGuard<'_>,
     ) -> hyperv::HvHypercallOutput;
 
-    /// Obtain CPUID using platform-specific tables.
-    fn cpuid(eax: u32, ecx: u32) -> Option<CpuidResult>
-    where
-        Self: Sized,
-    {
-        // SAFETY: CPUID is always safe
-        unsafe { Some(__cpuid_count(eax, ecx)) }
-    }
-
     /// Write a host-owned MSR.
     /// # Safety
     /// The caller must ensure that the requested MSR modification does mot
@@ -371,21 +362,8 @@ macro_rules! platform_method {
 }
 
 #[inline]
-pub fn cpuid(leaf: u32, subleaf: u32) -> Option<CpuidResult> {
-    match *SVSM_PLATFORM_TYPE {
-        SvsmPlatformType::Native => <NativePlatform as SvsmPlatform>::cpuid(leaf, subleaf),
-        SvsmPlatformType::Snp => <SnpPlatform as SvsmPlatform>::cpuid(leaf, subleaf),
-        SvsmPlatformType::Tdp => <TdpPlatform as SvsmPlatform>::cpuid(leaf, subleaf),
-    }
-}
-
-#[inline]
-pub fn cpuid_feature(feature: &CpuidFeature) -> Option<CpuidResult> {
-    match *SVSM_PLATFORM_TYPE {
-        SvsmPlatformType::Native => <NativePlatform as CpuidBackend>::cpuid(feature),
-        SvsmPlatformType::Snp => <SnpPlatform as CpuidBackend>::cpuid(feature),
-        SvsmPlatformType::Tdp => <TdpPlatform as CpuidBackend>::cpuid(feature),
-    }
+pub fn cpuid(feature: &CpuidFeature) -> Option<CpuidResult> {
+    platform_method!(cpuid, feature)
 }
 
 #[inline]

kernel/src/platform/mod.rs

@@ -26,7 +26,7 @@ use crate::cpu::x86::{
 use crate::error::SvsmError;
 use crate::hyperv::{self, hyperv_start_cpu, is_hyperv_host};
 use crate::io::{DEFAULT_IO_DRIVER, IOPort};
-use crate::platform::{cpuid_feature, cpuid_value_or, has_cpuid_feature};
+use crate::platform::{cpuid, cpuid_value_or, has_cpuid_feature};
 #[cfg(debug_assertions)]
 use crate::types::PageSize;
 use crate::utils::MemoryRegion;
@@ -89,7 +89,7 @@ impl SvsmPlatform for NativePlatform {
     }
 
     fn get_cpu_vendor(&self) -> CpuVendor {
-        match cpuid_feature(&MAX_STD_LEAF).map(|r| r.edx) {
+        match cpuid(&MAX_STD_LEAF).map(|r| r.edx) {
             Some(0x6974_6e65) => CpuVendor::AMD,
             Some(0x4965_6e69) => CpuVendor::Intel,
             _ => CpuVendor::Unknown,

kernel/src/platform/native.rs

@@ -299,20 +299,6 @@ impl SvsmPlatform for SnpPlatform {
         })
     }
 
-    fn cpuid(eax: u32, ecx: u32) -> Option<CpuidResult>
-    where
-        Self: Sized,
-    {
-        // If this is an architectural CPUID leaf, then extract the result
-        // from the CPUID table.  Otherwise, request the value from the
-        // hypervisor.
-        if (eax >> 28) == 4 {
-            current_ghcb().cpuid(eax, ecx).ok()
-        } else {
-            cpuid_table(eax, ecx)
-        }
-    }
-
     unsafe fn write_host_msr(&self, msr: u32, value: u64) {
         current_ghcb()
             .wrmsr(msr, value)