linux-kernel - Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in vmx_cpu

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Date:	Mon, 8 Feb 2016 16:09:35 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Bruce Rogers <brogers@...e.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	jan.kiszka@...mens.com, namit@...technion.ac.il
Subject: Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in
 vmx_cpu_reset



On 03/02/2016 23:51, Bruce Rogers wrote:
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index e2951b6..21507b4 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -4993,8 +4993,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>  		vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->vpid);
>  
>  	cr0 = X86_CR0_NW | X86_CR0_CD | X86_CR0_ET;
> -	vmx_set_cr0(vcpu, cr0); /* enter rmode */
>  	vmx->vcpu.arch.cr0 = cr0;
> +	vmx_set_cr0(vcpu, cr0); /* enter rmode */

Your comment that the assignment is redundant is correct, but I am
afraid that this fix is also wrong.  In particular, it would not cause
exit_lmode and enter_rmode to be called.

You are not describing which call to kvm_mmu_reset_context was messed
up, so I'm not sure how your patch is fixing things.

Paolo