linux-kernel - Re: [RFC Part2 PATCH v3 13/26] KVM: SVM: Add KVM_SEV

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Date:   Wed, 13 Sep 2017 11:23:26 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...e.de>
Cc:     brijesh.singh@....com, linux-kernel@...r.kernel.org,
        x86@...nel.org, kvm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Joerg Roedel <joro@...tes.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        \"Radim Krčmář\" <rkrcmar@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RFC Part2 PATCH v3 13/26] KVM: SVM: Add KVM_SEV_INIT command

Hi Boris,

thanks for the detail review.

On 09/13/2017 10:06 AM, Borislav Petkov wrote:
...

>> +static int sev_platform_get_state(int *state, int *error)
>> +{
>> +	int ret;
>> +	struct sev_data_status *data;
>> +
>> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> 
> It's a bit silly to do the allocation only for the duration of
> sev_platform_status() - just allocate "data" on the stack.
> 

I am okay with moving it on the stack but just to give context why
I went in this way. The physical address of data is given to the
device (in this case SEV FW). I was not sure if its okay to pass the
stack address to the device. Additionally, the FW spec requires us to
zero all the fields -- so we need to memset if we allocate it on the
stack.