Re: [Xen-devel] [PATCH v3 1/2] x86/hvm: introduce cr{0, 4}_host_mask to store trapped bits of CR accesses

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 02/20/2018 03:56 AM, Roger Pau Monne wrote:
> At the moment this is currently set at VMC{S/B} creation and not changed,
> but further patches are going to change the CR4 mask at runtime.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> ---
> Changes since v2:
>  - Introduce masks only for CR4 and CR0.
>
> Changes since v1:
>  - New in this version.
> ---
>  xen/arch/x86/hvm/svm/vmcb.c    | 1 +
>  xen/arch/x86/hvm/vmx/vmcs.c    | 1 +
>  xen/include/asm-x86/hvm/vcpu.h | 4 ++++
>  3 files changed, 6 insertions(+)
>
> diff --git a/xen/arch/x86/hvm/svm/vmcb.c b/xen/arch/x86/hvm/svm/vmcb.c
> index 0e6cba5b7b..beeafad235 100644
> --- a/xen/arch/x86/hvm/svm/vmcb.c
> +++ b/xen/arch/x86/hvm/svm/vmcb.c
> @@ -169,6 +169,7 @@ static int construct_vmcb(struct vcpu *v)
>      vmcb->tr.base = 0;
>      vmcb->tr.limit = 0xff;
>  
> +    v->arch.hvm_vcpu.cr0_host_mask = v->arch.hvm_vcpu.cr4_host_mask = ~0UL;
>      v->arch.hvm_vcpu.guest_cr[0] = X86_CR0_PE | X86_CR0_ET;
>      hvm_update_guest_cr(v, 0);


Is there a reason for setting those fields? SVM won't use them, will it?


-boris



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