KVM: x86: Fix emulated CPUID features being applied to wrong sub-leaf

Browse source

Pass the CPUID index into cpuid_func_emulated() and return no emulated
features for indexed CPUID leaves with a non-zero index.

KVM currently emulates CPUID features only for index 0, but
kvm_vcpu_after_set_cpuid() looks up emulated features by function alone.
As a result, reverse_cpuid[] entries that share a function but use a
non-zero index, e.g. CPUID.7.1:ECX, can inherit emulated features that
belong to index 0.  For example, RDPID, which is CPUID.7.0:ECX[22], can
be incorrectly OR'd into CPUID.7.1:ECX.

This is benign today because the affected bits do not correspond to
features KVM cares about, but it can become a real bug as new CPUID
features are defined.  Make the helper index-aware so emulated features
are applied only to the CPUID entry they actually describe.

Fixes: e592ec657d ("KVM: x86: Initialize guest cpu_caps based on KVM support")
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://patch.msgid.link/20260609075748.612704-1-binbin.wu@linux.intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

...

This commit is contained in:

Binbin Wu 2026-06-09 15:57:48 +08:00 • committed by Sean Christopherson

parent eb606a2438

commit 8835a24a56

1 changed files with 8 additions and 4 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

12

arch/x86/kvm/cpuid.c

View file