linux-kernel - Re: [PATCH 3/4] KVM: SVM: Adjust MMIO masks (for caching) before doing SEV(-ES) setup

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Date:   Fri, 29 Jul 2022 14:06:05 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michael Roth <michael.roth@....com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH 3/4] KVM: SVM: Adjust MMIO masks (for caching) before
 doing SEV(-ES) setup

On Thu, 2022-07-28 at 22:17 +0000, Sean Christopherson wrote:
> Adjust KVM's MMIO masks to account for the C-bit location prior to doing
> SEV(-ES) setup.  A future patch will consume enable_mmio caching during
> SEV setup as SEV-ES _requires_ MMIO caching, i.e. KVM needs to disallow
> SEV-ES if MMIO caching is disabled.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/svm/svm.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index aef63aae922d..62e89db83bc1 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -5034,13 +5034,16 @@ static __init int svm_hardware_setup(void)
>  	/* Setup shadow_me_value and shadow_me_mask */
>  	kvm_mmu_set_me_spte_mask(sme_me_mask, sme_me_mask);
>  
> -	/* Note, SEV setup consumes npt_enabled. */
> +	svm_adjust_mmio_mask();
> +
> +	/*
> +	 * Note, SEV setup consumes npt_enabled and enable_mmio_caching (which
> +	 * may be modified by svm_adjust_mmio_mask()).
> +	 */
>  	sev_hardware_setup();

If I am not seeing mistakenly, the code in latest queue branch doesn't consume
enable_mmio_caching.  It is only added in your later patch.

So perhaps adjust the comment or merge patches together?

>  
>  	svm_hv_hardware_setup();
>  
> -	svm_adjust_mmio_mask();
> -
>  	for_each_possible_cpu(cpu) {
>  		r = svm_cpu_init(cpu);
>  		if (r)