linux-kernel - Re: [Part2 PATCH v6 13/38] crypto: ccp: Add Secure Encrypted Virtualization (SEV) command support

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Message-ID: <20171026135614.GA12359@nazgul.tnic>
Date:   Thu, 26 Oct 2017 15:56:14 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     kvm@...r.kernel.org, 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, linux-kernel@...r.kernel.org
Subject: Re: [Part2 PATCH v6 13/38] crypto: ccp: Add Secure Encrypted
 Virtualization (SEV) command support

On Mon, Oct 23, 2017 at 02:57:04PM -0500, Brijesh Singh wrote:
> Calling PLATFORM_GET_STATUS is not required, we can manage the state through
> a simple ref count variable. Issuing PSP commands will always be much more
> expensive compare to accessing a protected global variable.

What does "protected" mean here?

In any case, that variable can be a simple bool as you use it as such.

> I would prefer to avoid invoking PSP command if possible.
> Additionally, the global semaphore is still needed to serialize
> the sev_platform_init() and sev_platform_shutdown() from multiple
> processes. e.g If process "A" calls sev_platform_init() and if it gets
> preempted due to whatever reason then we don't want another process
> to issue the shutdown command while process "A" is in middle of
> sev_platform_init().

How? You're holding fw_init_mutex.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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