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SubjectRe: [PATCH RFC v8 34/56] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_START command
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On 4/26/23 12:06, Sabin Rapan wrote:
> On 20.02.2023 20:38, Michael Roth wrote:
>> From: Brijesh Singh <brijesh.singh@amd.com>
>>
>>
>> +static int snp_decommission_context(struct kvm *kvm)
>> +{
>> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
>> + struct sev_data_snp_addr data = {};
>> + int ret;
>> +
>> + /* If context is not created then do nothing */
>> + if (!sev->snp_context)
>> + return 0;
>> +
>> + data.gctx_paddr = __sme_pa(sev->snp_context);
>> + ret = sev_do_cmd(SEV_CMD_SNP_DECOMMISSION, &data, NULL);
>> + if (WARN_ONCE(ret, "failed to release guest context"))
>> + return ret;
>> +
>> + /* free the context page now */
>> + snp_free_firmware_page(sev->snp_context);
>> + sev->snp_context = NULL;
>> +
>> + return 0;
>> +}
>> +
>
> Even though it's not documented, SNP_DECOMMISSION seems to clear the
> WBINVD indicator just like DEACTIVATE does for SEV.
> Won't ASID recycling race with SNP_DECOMMISSION if the latter isn't
> guarded with sev_deactivate_lock?

Good catch, yes, this needs to use the sev_deactivate_lock around the
DECOMMISSION command.

Thanks,
Tom

>
>
>> void sev_vm_destroy(struct kvm *kvm)
>> {
>> struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
>> @@ -2333,7 +2440,15 @@ void sev_vm_destroy(struct kvm *kvm)
>> }
>> }
>>
>> - sev_unbind_asid(kvm, sev->handle);
>> + if (sev_snp_guest(kvm)) {
>> + if (snp_decommission_context(kvm)) {
>> + WARN_ONCE(1, "Failed to free SNP guest context, leaking asid!\n");
>> + return;
>> + }
>> + } else {
>> + sev_unbind_asid(kvm, sev->handle);
>> + }
>> +
>> sev_asid_free(sev);
>> }
>>
>
>
>
> Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.

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