Re: [PATCH 1/3 v3] KVM: x86: Create mask for guest CR4 reserved bits in kvm_update_cpuid()

[Sean Christopherson <sean.j.christopherson@xxxxxxxxx>]

On Fri, May 15, 2020 at 01:36:07AM -0400, Krish Sadhukhan wrote:
> Instead of creating the mask for guest CR4 reserved bits in kvm_valid_cr4(),
> do it in kvm_update_cpuid() so that it can be reused instead of creating it
> each time kvm_valid_cr4() is called.
> 
> Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
> ---
>  arch/x86/include/asm/kvm_host.h |  2 ++
>  arch/x86/kvm/cpuid.c            |  2 ++
>  arch/x86/kvm/x86.c              | 24 ++----------------------
>  arch/x86/kvm/x86.h              | 21 +++++++++++++++++++++
>  4 files changed, 27 insertions(+), 22 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 42a2d0d..e2d9e4b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -820,6 +820,8 @@ struct kvm_vcpu_arch {
>  
>  	/* AMD MSRC001_0015 Hardware Configuration */
>  	u64 msr_hwcr;
> +
> +	u64 guest_cr4_reserved_bits;

This can be an 'unsigned long', the u64 type in the existing code is a goof
on my part.  I'd also vote to co-locate it with the other cr4 variables and
abbreviate reserved to keep the name manageable, e.g.

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index ae6a93ed83d39..21ece121e1858 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -573,6 +573,7 @@ struct kvm_vcpu_arch {
        unsigned long cr3;
        unsigned long cr4;
        unsigned long cr4_guest_owned_bits;
+       unsigned long cr4_guest_rsvd_bits;
        unsigned long cr8;
        u32 pkru;
        u32 hflags;