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

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Message-ID: <20171012222202.qvso6kyvetbt4oco@pd.tnic>
Date:   Fri, 13 Oct 2017 00:22:02 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     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 Thu, Oct 12, 2017 at 04:52:32PM -0500, Brijesh Singh wrote:
> See my above comment, I think the simplest solution is remove psp->sev_misc

Ok, so far so good.

But now you still need to track which is the last psp device and to call
misc_deregister() only when the last device exits. Because if you do
that for the first psp device as it is now, all the following devices
will see a deregistered misc device. And I don't think we want that.

You probably could do something with reference counting: Documentation/kref.txt
to track that and have the last device deregister the misc device.

Or have the "enclosing" sp-dev deregister the misc device when it is
exiting and when it is sure that there are no more psp devices...

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--