fix(vmm): pass through cache information from host

4.14 KVM reports the supported leaf 0x80000006 as zeroes,
so it needs to be passed through from the host CPUID so that
the guest sees meaningful information about the caches.

Signed-off-by: Nikita Kalyazin <[email protected]>

Author: kalyazin

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed passing through cache information from host in CPUID leaf 0x80000006.
+
 ## [1.3.2]
 
 ### Fixed

src/cpuid/src/cpu_leaf.rs

@@ -313,6 +313,16 @@ pub mod leaf_0x80000001 {
     }
 }
 
+pub mod leaf_0x80000006 {
+    pub const LEAF_NUM: u32 = 0x8000_0006;
+
+    pub mod edx {
+        use crate::bit_helper::BitRange;
+
+        pub const RESERVED_BITRANGE: BitRange = bit_range!(16, 17);
+    }
+}
+
 pub mod leaf_0x80000008 {
     pub const LEAF_NUM: u32 = 0x8000_0008;
 

src/cpuid/src/transformer/amd.rs

@@ -132,6 +132,7 @@ impl CpuidTransformer for AmdCpuidTransformer {
         // Some versions of kernel may return the 0xB leaf for AMD even if this is an
         // Intel-specific leaf. Remove it.
         cpuid.retain(|entry| entry.function != leaf_0xb::LEAF_NUM);
+        use_host_cpuid_function(cpuid, leaf_0x80000006::LEAF_NUM, false)?;
         use_host_cpuid_function(cpuid, leaf_0x8000001e::LEAF_NUM, false)?;
         use_host_cpuid_function(cpuid, leaf_0x8000001d::LEAF_NUM, true)?;
         self.process_entries(cpuid, vm_spec)
@@ -143,6 +144,7 @@ impl CpuidTransformer for AmdCpuidTransformer {
             leaf_0x7::LEAF_NUM => Some(amd::update_structured_extended_entry),
             leaf_0x80000000::LEAF_NUM => Some(amd::update_largest_extended_fn_entry),
             leaf_0x80000001::LEAF_NUM => Some(amd::update_extended_feature_info_entry),
+            leaf_0x80000006::LEAF_NUM => Some(common::update_extended_cache_features_entry),
             leaf_0x80000008::LEAF_NUM => Some(amd::update_amd_features_entry),
             leaf_0x8000001d::LEAF_NUM => Some(amd::update_extended_cache_topology_entry),
             leaf_0x8000001e::LEAF_NUM => Some(amd::update_extended_apic_id_entry),

src/cpuid/src/transformer/common.rs

@@ -98,6 +98,19 @@ pub fn update_cache_parameters_entry(
     Ok(())
 }
 
+pub fn update_extended_cache_features_entry(
+    entry: &mut kvm_cpuid_entry2,
+    _vm_spec: &VmSpec,
+) -> Result<(), Error> {
+    use crate::cpu_leaf::leaf_0x80000006::*;
+
+    // This only zeroes reserved bits [17:16].
+    // The actual pass through is done by the `use_host_cpuid_function()` call.
+    entry.edx.write_bits_in_range(&edx::RESERVED_BITRANGE, 0);
+
+    Ok(())
+}
+
 /// Replaces the `cpuid` entries corresponding to `function` with the entries from the host's cpuid.
 pub fn use_host_cpuid_function(
     cpuid: &mut CpuId,

src/cpuid/src/transformer/intel.rs

@@ -4,6 +4,7 @@
 use super::*;
 use crate::bit_helper::BitHelper;
 use crate::cpu_leaf::*;
+use crate::transformer::common::use_host_cpuid_function;
 
 // The APIC ID shift in leaf 0xBh specifies the number of bits to shit the x2APIC ID to get a
 // unique topology of the next level. This allows 128 logical processors/package.
@@ -139,6 +140,8 @@ impl CpuidTransformer for IntelCpuidTransformer {
                 .map_err(Error::Fam)?;
         }
 
+        use_host_cpuid_function(cpuid, leaf_0x80000006::LEAF_NUM, false)?;
+
         self.process_entries(cpuid, vm_spec)
     }
 
@@ -150,6 +153,7 @@ impl CpuidTransformer for IntelCpuidTransformer {
             leaf_0xa::LEAF_NUM => Some(intel::update_perf_mon_entry),
             leaf_0xb::LEAF_NUM => Some(intel::update_extended_topology_entry),
             0x8000_0002..=0x8000_0004 => Some(common::update_brand_string_entry),
+            leaf_0x80000006::LEAF_NUM => Some(common::update_cache_parameters_entry),
             _ => None,
         }
     }