Re: [PATCH v5 02/15] KVM: SVM: Free sev_asid_bitmap during init if SEV setup fails

Tom Lendacky
2021-04-22T19:34:41Z

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@amd.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

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