linux-kernel - Re: [PATCH v5 02/15] KVM: SVM: Free sev_asid

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Message-ID: <1f3f3ccf-a6af-3ea4-3109-5d38897f820e@amd.com>
Date:   Thu, 22 Apr 2021 14:34:33 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Borislav Petkov <bp@...e.de>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v5 02/15] KVM: SVM: Free sev_asid_bitmap during init if
 SEV setup fails

On 4/21/21 9:11 PM, Sean Christopherson wrote:
> Free sev_asid_bitmap if the reclaim bitmap allocation fails, othwerise
> KVM will unnecessarily keep the bitmap when SEV is not fully enabled.
> 
> Freeing the page is also necessary to avoid introducing a bug when a
> future patch eliminates svm_sev_enabled() in favor of using the global
> 'sev' flag directly.  While sev_hardware_enabled() checks max_sev_asid,
> which is true even if KVM setup fails, 'sev' will be true if and only
> if KVM setup fully succeeds.
> 
> Fixes: 33af3a7ef9e6 ("KVM: SVM: Reduce WBINVD/DF_FLUSH invocations")
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>  arch/x86/kvm/svm/sev.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index b4e471b0a231..5ff8a202cc01 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1788,8 +1788,11 @@ void __init sev_hardware_setup(void)
>  		goto out;
>  
>  	sev_reclaim_asid_bitmap = bitmap_zalloc(max_sev_asid, GFP_KERNEL);
> -	if (!sev_reclaim_asid_bitmap)
> +	if (!sev_reclaim_asid_bitmap) {
> +		bitmap_free(sev_asid_bitmap);
> +		sev_asid_bitmap = NULL;
>  		goto out;
> +	}
>  
>  	pr_info("SEV supported: %u ASIDs\n", max_sev_asid - min_sev_asid + 1);
>  	sev_supported = true;
>