KVM: x86: Dynamically allocate per-vCPU emulation context

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Allocate the emulation context instead of embedding it in struct
kvm_vcpu_arch.

Dynamic allocation provides several benefits:

  - Shrinks the size x86 vcpus by ~2.5k bytes, dropping them back below
    the PAGE_ALLOC_COSTLY_ORDER threshold.
  - Allows for dropping the include of kvm_emulate.h from asm/kvm_host.h
    and moving kvm_emulate.h into KVM's private directory.
  - Allows a reducing KVM's attack surface by shrinking the amount of
    vCPU data that is exposed to usercopy.
  - Allows a future patch to disable the emulator entirely, which may or
    may not be a realistic endeavor.

Mark the entire struct as valid for usercopy to maintain existing
behavior with respect to hardened usercopy.  Future patches can shrink
the usercopy range to cover only what is necessary.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

...

This commit is contained in:

Sean Christopherson 2020-02-18 15:29:48 -08:00 • committed by Paolo Bonzini

parent f0ed4760ed

commit c9b8b07cde

4 changed files with 61 additions and 17 deletions

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1

arch/x86/include/asm/kvm_emulate.h

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2

arch/x86/include/asm/kvm_host.h

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10

arch/x86/kvm/trace.h

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65

arch/x86/kvm/x86.c

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