KVM: x86: Initialize guest cpu_caps based on guest CPUID

Browse source

Initialize a vCPU's capabilities based on the guest CPUID provided by
userspace instead of simply zeroing the entire array.  This is the first
step toward using cpu_caps to query *all* CPUID-based guest capabilities,
i.e. will allow converting all usage of guest_cpuid_has() to
guest_cpu_cap_has().

Zeroing the array was the logical choice when using cpu_caps was opt-in,
e.g. "unsupported" was generally a safer default, and the whole point of
governed features is that KVM would need to check host and guest support,
i.e. making everything unsupported by default didn't require more code.

But requiring KVM to manually "enable" every CPUID-based feature in
cpu_caps would require an absurd amount of boilerplate code.

Follow existing CPUID/kvm_cpu_caps nomenclature where possible, e.g. for
the change() and clear() APIs.  Replace check_and_set() with constrain()
to try and capture that KVM is constraining userspace's desired guest
feature set based on KVM's capabilities.

This is intended to be gigantic nop, i.e. should not have any impact on
guest or KVM functionality.

This is also an intermediate step; a future commit will also incorporate
KVM support into the vCPU's cpu_caps before converting guest_cpuid_has()
to guest_cpu_cap_has().

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-42-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

...

This commit is contained in:

Sean Christopherson 2024-11-27 17:34:08 -08:00

parent 7ea34578ae

commit a7a308f863

4 changed files with 85 additions and 21 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

46

arch/x86/kvm/cpuid.c

View file

24

arch/x86/kvm/cpuid.h

View file

28

arch/x86/kvm/svm/svm.c

View file

8

arch/x86/kvm/vmx/vmx.c

View file