linux-kernel - Re: [PATCH 05/13] KVM: x86: pass host_initiated to functions that read MSRs

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Date:	Mon, 4 May 2015 16:01:43 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org, bsd@...hat.com,
	guangrong.xiao@...ux.intel.com,
	Yang Zhang <yang.z.zhang@...el.com>, wanpeng.li@...ux.intel.com
Subject: Re: [PATCH 05/13] KVM: x86: pass host_initiated to functions that
 read MSRs

2015-04-30 13:36+0200, Paolo Bonzini:
> SMBASE is only readable from SMM for the VCPU, but it must be always
> accessible if userspace is accessing it.  Thus, all functions that
> read MSRs are changed to accept a struct msr_data; the host_initiated
> and index fields are pre-initialized, while the data field is filled
> on return.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> @@ -1048,6 +1048,21 @@ EXPORT_SYMBOL_GPL(kvm_set_msr);
>  /*
>   * Adapt set_msr() to msr_io()'s calling convention
>   */
> +static int do_get_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
> +{
> +	struct msr_data msr;
> +	int r;
> +
> +	msr.index = index;
> +	msr.host_initiated = true;
> +	r = kvm_set_msr(vcpu, &msr);

Should be kvm_get_msr().

> +	if (r)
> +		return r;
> +
> +	*data = msr.data;
> +	return 0;
> +}
> +
> @@ -3456,7 +3470,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>  		break;
>  	}
>  	case KVM_GET_MSRS:
> -		r = msr_io(vcpu, argp, kvm_get_msr, 1);
> +		r = msr_io(vcpu, argp, do_get_msr, 1);
>  		break;
>  	case KVM_SET_MSRS:
>  		r = msr_io(vcpu, argp, do_set_msr, 0);
> @@ -4948,7 +4962,17 @@ static void emulator_set_segment(struct x86_emulate_ctxt *ctxt, u16 selector,
>  static int emulator_get_msr(struct x86_emulate_ctxt *ctxt,
>  			    u32 msr_index, u64 *pdata)
>  {
> -	return kvm_get_msr(emul_to_vcpu(ctxt), msr_index, pdata);
> +	struct msr_data msr;
> +	int r;
> +
> +	msr.index = msr_index;
> +	msr.host_initiated = false;
> +	r = kvm_get_msr(emul_to_vcpu(ctxt), &msr);
> +	if (r)
> +		return r;
> +
> +	*pdata = msr.data;
> +	return 0;
>  }

(Only msr.host_initiated changed from do_get_msr() ...
 I'd add a function with an extra bool arg and call it twice.)
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