linux-kernel - Re: [PATCH v5 02/34] KVM: SVM: Remove the call to sev_platform

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Date:   Mon, 14 Dec 2020 10:45:20 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v5 02/34] KVM: SVM: Remove the call to
 sev_platform_status() during setup

On 12/14/20 6:29 AM, Paolo Bonzini wrote:
> On 10/12/20 18:09, Tom Lendacky wrote:
>> From: Tom Lendacky <thomas.lendacky@....com>
>>
>> When both KVM support and the CCP driver are built into the kernel instead
>> of as modules, KVM initialization can happen before CCP initialization. As
>> a result, sev_platform_status() will return a failure when it is called
>> from sev_hardware_setup(), when this isn't really an error condition.
>>
>> Since sev_platform_status() doesn't need to be called at this time anyway,
>> remove the invocation from sev_hardware_setup().
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>>   arch/x86/kvm/svm/sev.c | 22 +---------------------
>>   1 file changed, 1 insertion(+), 21 deletions(-)
>>
>> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
>> index c0b14106258a..a4ba5476bf42 100644
>> --- a/arch/x86/kvm/svm/sev.c
>> +++ b/arch/x86/kvm/svm/sev.c
>> @@ -1127,9 +1127,6 @@ void sev_vm_destroy(struct kvm *kvm)
>>     int __init sev_hardware_setup(void)
>>   {
>> -    struct sev_user_data_status *status;
>> -    int rc;
>> -
>>       /* Maximum number of encrypted guests supported simultaneously */
>>       max_sev_asid = cpuid_ecx(0x8000001F);
>>   @@ -1148,26 +1145,9 @@ int __init sev_hardware_setup(void)
>>       if (!sev_reclaim_asid_bitmap)
>>           return 1;
>>   -    status = kmalloc(sizeof(*status), GFP_KERNEL);
>> -    if (!status)
>> -        return 1;
>> -
>> -    /*
>> -     * Check SEV platform status.
>> -     *
>> -     * PLATFORM_STATUS can be called in any state, if we failed to query
>> -     * the PLATFORM status then either PSP firmware does not support SEV
>> -     * feature or SEV firmware is dead.
>> -     */
>> -    rc = sev_platform_status(status, NULL);
>> -    if (rc)
>> -        goto err;
>> -
>>       pr_info("SEV supported\n");
>>   -err:
>> -    kfree(status);
>> -    return rc;
>> +    return 0;
>>   }
>>     void sev_hardware_teardown(void)
>>
> 
> Queued with Cc: stable.
> 
> Note that sev_platform_status now can become static within
> drivers/crypto/ccp/sev-dev.c.

Nice catch. I'll look at doing a follow-on patch to change that.

Thanks,
Tom

> 
> Paolo