linux-kernel - Re: [Part2 PATCH v5.2 12.2/31] crypto: ccp: Add Secure Encrypted Virtualization (SEV) command support

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Date:   Thu, 12 Oct 2017 16:52:32 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...e.de>
Cc:     brijesh.singh@....com, Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Gary Hook <gary.hook@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        linux-crypto@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Part2 PATCH v5.2 12.2/31] crypto: ccp: Add Secure Encrypted
 Virtualization (SEV) command support


On 10/12/17 4:41 PM, Borislav Petkov wrote:
> On Thu, Oct 12, 2017 at 04:11:18PM -0500, Brijesh Singh wrote:
>> The sev_exit() will be called for all the psp_device instance. we need
>> to set psp_misc_dev = NULL after deregistering the device.
>>
>> if (psp_misc_dev) {
>>   misc_deregister(psp_misc_dev);
>>    psp_misc_dev = NULL;
> Right, except we assign that misc device to every psp device:
>
> 	psp->sev_misc = psp_misc_dev;
>
> so the question now is, how do you want this to work: the misc device
> should be destroyed after the last psp device is destroyed or how?

We don't know when the last psp device is getting destroyed. Since we
are  making the sev_misc_dev as a global variable then there is no
reason for 'sev_misc' field in the psp_device.

> Because after the first:
>
> 	psp_misc_dev = NULL;
>
> the respective psp->sev_misc will still keep references to that device
> but the device itself will be already deregistered. And that sounds
> strange.

See my above comment, I think the simplest solution is remove psp->sev_misc