Re: [PATCH v2 02/14] KVM: SVM: Free sev_asid_bitmap during init if SEV setup fails

[Tom Lendacky]

On 1/13/21 6:36 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@xxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>   arch/x86/kvm/svm/sev.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index c8ffdbc81709..0eeb6e1b803d 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1274,8 +1274,10 @@ 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);

Until that future change, you probably need to do sev_asid_bitmap = NULL 
here to avoid an issue in sev_hardware_teardown() when it tries to free it 
again.

Thanks,
Tom

>   		goto out;
> +	}
>   
>   	pr_info("SEV supported: %u ASIDs\n", max_sev_asid - min_sev_asid + 1);
>   	sev_supported = true;