linux-kernel - Re: [PATCH v4 14/19] KVM: SVM: Check that the current CPU supports SVM in kvm_is_svm

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Date:   Mon, 24 Jul 2023 15:29:34 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Kai Huang <kai.huang@...el.com>, Chao Gao <chao.gao@...el.com>
Subject: Re: [PATCH v4 14/19] KVM: SVM: Check that the current CPU supports
 SVM in kvm_is_svm_supported()

Hi Sean,

On Fri, Jul 21, 2023 at 01:18:54PM -0700, Sean Christopherson wrote:
> +static bool kvm_is_svm_supported(void)
> +{
> +	bool supported;
> +
> +	migrate_disable();
> +	supported = __kvm_is_svm_supported();
> +	migrate_enable();

I am typically very wary of the constructs like this, as the value
returned is obsolete the moment migrate_enable() happens. Is value of
"svm was supported at some time in the past but may or may not be
supported right now" useful and if it is then could you add comment why?

Thanks.

-- 
Dmitry