Re: [PATCH 3/9] Implement GIF, clgi and stgi v5

[Anthony Liguori <anthony@codemonkey.ws>]

Alexander Graf wrote:
> This patch implements the GIF flag and the clgi and stgi instructions that
> set this flag. Only if the flag is set (default), interrupts can be received by
> the CPU.
>
> To keep the information about that somewhere, this patch adds a new hidden
> flags vector. that is used to store information that does not go into the
> vmcb, but is SVM specific.
>
> v2 moves the hflags to x86 generic code
> v3 makes use of the new permission helper
>
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
>  arch/x86/kvm/svm.c         |   42 +++++++++++++++++++++++++++++++++++++++---
>  include/asm-x86/kvm_host.h |    3 +++
>  2 files changed, 42 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index a00421b..62bfa2b 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -614,6 +614,8 @@ static void init_vmcb(struct vcpu_svm *svm)
>  		save->cr4 = 0;
>  	}
>  	force_new_asid(&svm->vcpu);
> +
> +	svm->vcpu.arch.hflags = HF_GIF_MASK;
>  }
>  
>  static int svm_vcpu_reset(struct kvm_vcpu *vcpu)
> @@ -1233,6 +1235,36 @@ static int nested_svm_do(struct vcpu_svm *svm,
>  	return retval;
>  }
>  
> +static int stgi_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
> +{
> +	if (nested_svm_check_permissions(svm))
> +		return 1;
> +
> +	svm->next_rip = kvm_rip_read(&svm->vcpu) + 3;
> +	skip_emulated_instruction(&svm->vcpu);
> +
> +	svm->vcpu.arch.hflags |= HF_GIF_MASK;
> +
> +	return 1;
> +}
>   

It feels a little strange to see this here instead of an implementation 
of stgi/clgi in x86_emulate.  Any reason for not going that route?

GIF somehow needs exposure to userspace too, right?  Otherwise, when 
using -no-kernel-apic, userspace may try to inject an interrupt when the 
guest cannot handle it, right?

Regards,

Anthony Liguori