linux-kernel - Re: [Part2 PATCH v6.1 16/38] crypto: ccp: Add Secure Encrypted Virtualization (SEV) command support

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Message-ID: <de5d7e77-56d0-8cbc-1dcb-01cf3f0daeb4@amd.com>
Date:   Mon, 30 Oct 2017 20:29:25 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...en8.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 v6.1 16/38] crypto: ccp: Add Secure Encrypted
 Virtualization (SEV) command support



On 10/30/17 12:57 PM, Borislav Petkov wrote:
> On Mon, Oct 30, 2017 at 12:49:14PM -0500, Brijesh Singh wrote:
>> If the buffer is allocated on the stack then there is no guarantee that
> static global is not allocated on the stack.

Okay, Just tried static global with CONFIG_VMAP_STACK=y and I am getting
wrong physical address with __pa. PSP command fails with error code
"INVALID_ADDRESS". The same thing works fine with kmalloc() buffer.

>> I can certainly move the allocation outside, but then it may increase the
>> code size in other functions. If its not a big deal then I would prefer to
>> keep what we have.
> Avoiding repeated k*alloc calls is always a good thing. Actually kmalloc-ing 20
> bytes each time sounds like it is not worth the calling overhead to me.
>

To avoid repeated k*alloc calls, I could devm_kzalloc() these variable 
during sev_init() and reuse them when needed.