linux-kernel - Re: [PATCH v6 40/42] virt: Add SEV-SNP guest driver

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Date:   Sun, 10 Oct 2021 20:51:17 +0300
From:   Dov Murik <dovmurik@...ux.ibm.com>
To:     Brijesh Singh <brijesh.singh@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        Dov Murik <dovmurik@...ux.ibm.com>
Subject: Re: [PATCH v6 40/42] virt: Add SEV-SNP guest driver

Hi Brijesh,

On 08/10/2021 21:04, Brijesh Singh wrote:
> SEV-SNP specification provides the guest a mechanisum to communicate with
> the PSP without risk from a malicious hypervisor who wishes to read, alter,
> drop or replay the messages sent. The driver uses snp_issue_guest_request()
> to issue GHCB SNP_GUEST_REQUEST or SNP_EXT_GUEST_REQUEST NAE events to
> submit the request to PSP.
> 
> The PSP requires that all communication should be encrypted using key
> specified through the platform_data.
> 
> The userspace can use SNP_GET_REPORT ioctl() to query the guest
> attestation report.
> 
> See SEV-SNP spec section Guest Messages for more details.
> 
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> ---
>  Documentation/virt/coco/sevguest.rst  |  77 ++++
>  drivers/virt/Kconfig                  |   3 +
>  drivers/virt/Makefile                 |   1 +
>  drivers/virt/coco/sevguest/Kconfig    |   9 +
>  drivers/virt/coco/sevguest/Makefile   |   2 +
>  drivers/virt/coco/sevguest/sevguest.c | 561 ++++++++++++++++++++++++++
>  drivers/virt/coco/sevguest/sevguest.h |  98 +++++
>  include/uapi/linux/sev-guest.h        |  44 ++
>  8 files changed, 795 insertions(+)
>  create mode 100644 Documentation/virt/coco/sevguest.rst
>  create mode 100644 drivers/virt/coco/sevguest/Kconfig
>  create mode 100644 drivers/virt/coco/sevguest/Makefile
>  create mode 100644 drivers/virt/coco/sevguest/sevguest.c
>  create mode 100644 drivers/virt/coco/sevguest/sevguest.h
>  create mode 100644 include/uapi/linux/sev-guest.h
> 

[...]


> +
> +static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
> +{
> +	u8 *key = NULL;
> +
> +	switch (id) {
> +	case 0:
> +		*seqno = &layout->os_area.msg_seqno_0;
> +		key = layout->vmpck0;
> +		break;
> +	case 1:
> +		*seqno = &layout->os_area.msg_seqno_1;
> +		key = layout->vmpck1;
> +		break;
> +	case 2:
> +		*seqno = &layout->os_area.msg_seqno_2;
> +		key = layout->vmpck2;
> +		break;
> +	case 3:
> +		*seqno = &layout->os_area.msg_seqno_3;
> +		key = layout->vmpck3;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return NULL;

This should be 'return key', right?

-Dov

> +}
> +